A method for allocation according to the economic behaviour in the EU-ETS for by-products used in cement industry

Purpose

The most efficient way to reduce the environmental impact of cement production is to replace Portland cement with alternative cementitious materials. These are most often industrial waste such as blast-furnace slags (GBFS) and coal combustion fly ashes (FA). However, a recent European directive no longer considers these products as waste but as by-products. Therefore, the impact of their production has to be considered. Within this new framework, this study develops an evaluation method of their environmental impacts.

Method

This paper presents pre-existing methods and underlines their limits. Through our evaluation of these methods, it has become clear that the allocation procedure is necessary; however, results depend highly on the chosen allocation procedure. This study presents a new allocation method, based on the fact that both cement and the alternative materials, GBFS and FA, are produced by energy-intensive industries (cement iron and coal) which are all subjected to the European Union Greenhouse Gas Emission Trading System. In this carbon trading system, it is economically beneficial for industries to reduce their environmental impact, like for when, by example, by-products from one industry are used as alternative ‘green’ material by another industry. Our allocation coefficient is calculated so that the economic gains and losses are the same for all of the industries involved in these exchanges and provides the overall environmental benefit of the exchanges.

Results and discussion

The discussion shows that whilst this method has much in common with other allocation methods, it is more accurate as it allocates the environmental costs fairly over the industries involved and is more robust because of its constant value. One of its limits is that it cannot be used for life cycle inventories; however, we test the possibility of choosing a coefficient from one impact category and applying it to all the others.

Conclusion

Lastly, the technical term of the equation this paper presents could be employed for consequential life cycle assessment, to calculate the most environmental uses by-products could be put to.     

Life cycle greenhouse gas emissions of electricity generation in the province of Ontario, Canada

Purpose

This paper assesses facility-specific life cycle greenhouse gas (GHG) emission intensities for electricity-generating facilities in the province of Ontario in 2008. It offers policy makers, researchers and other stakeholders of the Ontario electricity system with data regarding some of the environmental burdens from multiple generation technology currently deployed in the province.

Methods

Methods involved extraction of data and analysis from several publically accessible datasets, as well as from the LCA literature. GHG emissions data for operation of power plants came from the Government of Canada GHG registry and the Ontario Power Generation (OPG) Sustainable Development reports. Facility-specific generation data came from the Independent Electricity System Operator in Ontario and the OPG.

Results

Full life cycle GHG intensity (tonnes of CO₂ equivalent per gigawatt hour) estimates are provided for 4 coal facilities, 27 natural gas facilities, 1 oil/natural gas facility, 3 nuclear facilities, 7 run-of-river hydro facilities and 37 reservoir hydro facilities, and 7 wind facilities. Average (output weighted) life cycle GHG intensities are calculated for each fuel type in Ontario, and the life cycle GHG intensity for the Ontario grid as a whole (in 2008) is estimated to be 201 t CO₂e/GWh.

Conclusions

The results reflect only the global warming impact of electricity generation, and they are meant to inform a broader discussion which includes other environmental, social, cultural, institutional and economic factors. This full range of factors should be included in decisions regarding energy policy for the Province of Ontario, and in future work on the Ontario electricity system.     

Quantifying the greenhouse benefits of the use of wood products in two popular house designs in Sydney, Australia

Purpose

As the average wood products usage per unit of floor area in Australia has decreased significantly over time, there is potential for increased greenhouse gas (GHG) mitigation benefits through an increased use of wood products in buildings. This study determined the GHG outcomes of the extraction, manufacture, transport, use in construction, maintenance and disposal of wood products and other building materials for two popular house designs in Sydney, Australia.

Methods

The life cycle assessment (LCA) was undertaken using the computer model SimaPro 7.1, with the functional unit being the supply of base building elements for domestic houses in Sydney and its subsequent use over a 50-year period. The key data libraries used were the Australian Life Cycle Inventory library, the ecoinvent library (with data adapted to Australian circumstances where appropriate) and data for timber production from an Australian study for a range of Australian forestry production systems and wood products. Two construction variations were assessed: the original intended construction, and a “timber-maximised” alternative. The indicator assessed was global warming, as the focus was on GHG emissions, and the effect of timber production, use and disposal on the fate of carbon.

Results and discussion

The timber maximised design resulted in approximately half the GHG emissions associated with the base designs. The sub-floor had the largest greenhouse impact due to the concrete components, followed by the walls due to the usage of bricks. The use of a “timber maximised” design offset between 23 and 25 % of the total operational energy of the houses. Inclusion of carbon storage in landfill made a very significant difference to GHG outcomes, equivalent to 40–60 % of total house GHG emissions. The most beneficial options for disposal from a GHG perspective were landfill and incineration with energy recovery.

Conclusions

The study showed that significant GHG emission savings were achieved by optimising the use of wood products for two common house designs in Sydney. The switch of the sub-floor and floor covering components to a “wood” option accounted for most of the GHG savings. Inclusion of end of life parameters significantly impacted on the outcomes of the study.     

Carbon footprint and embodied energy assessment of a civil works program in a residential estate of Western Australia

Purpose

With building construction and demolition waste accounting for 50 % of land fill space, the diversion of reusable materials is essential for Perth”s environment. The reuse and recovery of embodied energy-intensive construction materials during civil engineering works programs can offer significant energy savings and assist in the mitigation of the carbon footprint.

Methods

A streamlined life cycle assessment, with limited focus, was carried out to determine the carbon footprint and embodied energy associated with a 100-m section of road base. A life cycle inventory of inputs (energy and materials) for all processes that occurred during the development of a 100-m road section was developed. Information regarding the energy and materials used for road construction work was obtained from the Perth-based firm, Cossill and Webley, Consulting Engineers. These inputs were inserted into Simapro LCA software to calculate the associated greenhouse gas emissions and embodied energy required for the construction and maintenance of a 100-m road section using. Two approaches were employed; a traditional approach that predominantly employed virgin materials, and a recycling approach.

Results and discussion

The GHG emissions and embodied energy associated with the construction of a 100-m road section using virgin materials are 180 tonnes of CO₂-e and 10.7 terajoules (TJ), respectively. The substitution of crushed rock with recycled brick road base does not appear to reduce the carbon footprint in the pre-construction stage (i.e. from mining to material construction, plus transportation of materials to the construction site). However, this replacement could potentially offer environmental benefits by reducing quarrying activities, which would not only conserve native bushland but also reduce the loss of biodiversity along with reducing the space and cost requirements associated with landfill. In terms of carbon footprint, it appears that GHG emissions are reduced significantly when using recycled asphalt, as opposed to other materials. About 22 to 30 % of greenhouse gas (GHG) emissions can be avoided by replacing 50 to 100 % of virgin asphalt with Reclaimed Asphalt Pavement (RAP) during the maintenance period.

Conclusions

The use of recycled building and road construction materials such as asphalt, concrete, and limestone can potentially reduce the embodied energy and greenhouse gas emissions associated with road construction. The recycling approach that uses 100 % reused crushed rock base and recycled concrete rubble, and 15 % RAP during the maintenance period could reduce the total carbon footprint by approximately 6 %. This large carbon saving in pavement construction is made possible by increasing the percentage of RAP in the wearing course.     

Life cycle assessment of sponge nickel produced by gas atomisation for use in industrial hydrogenation catalysis applications

Purpose

This paper presents a cradle-to-grave comparative life cycle assessment (LCA) of new gas atomised (GA) sponge nickel catalysts and evaluates their performance against the current cast and crush standard currently used in the industrial hydrogenation of butyraldehyde to butanol.

Methods

A comparative LCA has been made, accounting for the energy used and emissions throughout the entire life cycle of sponge nickel catalysts—ranging from the upstream production of materials (mainly aluminium and nickel), to the manufacturing, to the operation and finally to the recycling and disposal. The LCA was performed following ISO14040 principles where possible, and subsequently implemented in the software package GaBi 4.3. The CML2001 impact assessment methodology was used, with primary focus on comparing catalysts for equivalent greenhouse gasses generated over their lifetime and their relative global warming potential and secondary focus on acidification potential. This is justified as the lifetime is dominated by energy use in the operational phase, and acidification is dominated by the production of nickel for which existing ISO14040 collected data has been used. A sensitivity analysis was used to provide a number of scenarios and overall environmental performances of the various sponge nickels considered when compared to the existing industrial standard.

Results and discussion

It was found that the energy and emissions during the operation phase associated with a given catalyst significantly outweigh the primary production, manufacturing and recycling. Primary production of the nickel (and to a lesser extent molybdenum when used as a dopant) also has a significant environmental impact in terms of acidification potential, but this is offset by operational energy savings over the catalysts’ estimated lifetime and end of life recyclability. Finally, the impact of activity improvement and lifetime duration of sponge nickel catalysts was determined as both total life cycle energy for operational use and as a total life cycle global warming potential.

Conclusions

From this assessment, the newly developed, higher activity spongy nickel catalysts produced by gas atomisation could have a significantly lower environmental impact than the current industry standard cast and crush method. Given the potential environmental benefits of such catalysts, applications in other processes that require a catalyst should also be investigated.     

A new hybrid method for reducing the gap between WTW and LCA in the carbon footprint assessment of electric vehicles

Purpose

The well-to-wheel (WTW) methodology is widely used for policy support in road transport. It can be seen as a simplified life cycle assessment (LCA) that focuses on the energy consumption and CO₂ emissions only for the fuel being consumed, ignoring other stages of a vehicle’s life cycle. WTW results are therefore different from LCA results. In order to close this gap, the authors propose a hybrid WTW+LCA methodology useful to assess the greenhouse gas (GHG) profiles of road vehicles.

Methods

The proposed method (hybrid WTW+LCA) keeps the main hypotheses of the WTW methodology, but integrates them with LCA data restricted to the global warming potential (GWP) occurring during the manufacturing of the battery pack. WTW data are used for the GHG intensity of the EU electric mix, after a consistency check with the main life cycle impact (LCI) sources available in literature.

Results and discussion

A numerical example is provided, comparing GHG emissions due to the use of a battery electric vehicle (BEV) with emissions from an internal combustion engine vehicle. This comparison is done both according to the WTW approach (namely the JEC WTW version 4) and the proposed hybrid WTW+LCA method. The GHG savings due to the use of BEVs calculated with the WTW-4 range between 44 and 56 %, while according to the hybrid method the savings are lower (31–46 %). This difference is due to the GWP which arises as a result of the manufacturing of the battery pack for the electric vehicles.

Conclusions

The WTW methodology used in policy support to quantify energy content and GHG emissions of fuels and powertrains can produce results closer to the LCA methodology by adopting a hybrid WTW+LCA approach. While evaluating GHG savings due to the use of BEVs, it is important that this method considers the GWP due to the manufacturing of the battery pack.

     

Life cycle assessment of automotive lightweighting through polymers under US boundary conditions

Purpose

In the transportation sector, reducing vehicle weight is a cornerstone strategy to improve the fuel economy and energy efficiency of road vehicles. This study investigated the environmental implications of lightweighting two automotive parts (Ford Taurus front end bolster, Chevrolet Trailblazer/GMC Envoy assist step) using glass-fiber reinforced polymers (GFRP) instead of steel alloys.

Methods

The cradle-to-grave life cycle assessments (LCAs) for these studies consider a total service life of 150,000 miles for two applications: a 46 % lighter GFRP bolster on the 2010 Ford Taurus that replaced the 2008 steel and GFRP bolster, and a 51 % lighter GFRP running board for the 2007 Chevrolet Trailblazer/GMC Envoy that replaced the previous steel running board including its polymer fasteners. The life cycle stages in these critically reviewed and ISO-compliant LCA studies include the production of upstream materials and energy, product manufacturing, use, and the end-of-life treatment for all materials throughout the life cycle.

Results and discussion

The results show that the lighter GFRP products performed better than the steel products for global warming potential and primary energy demand for both case studies. In addition, the GFRP bolster performed better for acidification potential. The savings of fuel combustion and production during the use stage of a vehicle far outweigh the environmental impacts of manufacturing or end-of-life. An even greater benefit would be possible if the total weight reduction in the vehicle would be high enough to allow for the reduction of engine displacement or an elongation of gear ratio while maintaining constant vehicle dynamics. These so-called secondary measures allow the fuel savings per unit of mass to be more than doubled and are able to offset the slightly higher acidification potential of the GFRP running board which occurs when only the mass-induced fuel savings are considered.

Conclusions

The lightweight GFRP components are shown to outperform their steel counterparts over the full life cycle mainly due to the reduced fuel consumption of the vehicle in the use phase. To harvest the benefits of light weighting to their full extent, it is recommended that the sum of all mass reductions in the design process be monitored and, whenever feasible, invested into fuel economy by adapting the drive train while maintaining constant vehicle performance rather than leveraging the weight reduction to improve vehicle dynamics.     

Climate change impacts on life cycle greenhouse gas (GHG) emissions savings of biomethanol from corn and soybean

Purpose

The purpose of this study is to assess and calculate the potential impacts of climate change on the greenhouse gas (GHG) emissions reduction potentials of combined production of whole corn bioethanol and stover biomethanol, and whole soybean biodiesel and stalk biomethanol. Both fuels are used as substitutes to conventional fossil-based fuels. The product system includes energy crop (feedstock) production and transportation, biofuels processing, and biofuels distribution to service station.

Methods

The methodology is underpinned by life cycle thinking. Crop system model and life cycle assessment (LCA) model are linked in the analysis. The Decision Support System for Agrotechnology Transfer – crop system model (DSSAT-CSM) is used to simulate biomass and grain yield under different future climate scenarios generated using a combination of temperature, precipitation, and atmospheric CO₂. Historical weather data for Gainesville, Florida, are obtained for the baseline period (1981–1990). Daily minimum and maximum air temperatures are projected to increase by +2.0, +3.0, +4.0, and +5.0 °C, precipitation is projected to change by ±20, 10, and 5 %, and atmospheric CO₂ concentration is projected to increase by +70, +210, and +350 ppm. All projections are made throughout the growing season. GaBi 4.4 is used as primary LCA modelling software using crop yield data inputs from the DSSAT-CSM software. The models representation of the physical processes inventory (background unit processes) is constructed using the ecoinvent life cycle inventory database v2.0.

Results and discussion

Under current baseline climate condition, net greenhouse gas (GHG) emissions savings per hectare from corn-integrated biomethanol synthesis (CIBM) and soybean-integrated biomethanol synthesis (SIBM) were calculated as ?8,573.31 and ?3,441 kg CO₂-eq. ha^?1 yr^?1, respectively. However, models predictions suggest that these potential GHG emissions savings would be impacted by changing climate ranging from negative to positive depending on the crop and biofuel type, and climate scenario. Increased atmospheric level of CO₂ tends to minimise the negative impacts of increased temperature.

Conclusions

While policy measures are being put in place for the use of renewable biofuels driven by the desire to reduce GHG emissions from the use of conventional fossil fuels, climate change would also have impacts on the potential GHG emissions reductions resulting from the use of these renewable biofuels. However, the magnitude of the impact largely depends on the biofuel processing technology and the energy crop (feedstock) type.     

European renewable energy directive: Critical analysis of important default values and methods for calculating greenhouse gas (GHG) emissions of palm oil biodiesel

Purpose

The aim of this paper is to evaluate assumptions and data used in calculations  related to palm oil produced for biodiesel production relative to the European Renewable Energy Directive (EU-RED). The intent of this paper is not to review all assumptions and data, but rather to evaluate whether the methodology is applied in a consistent way and whether current default values address relevant management practices of palm oil production systems.

Methods

The GHG calculation method provided in Annex V of the EU-RED was used to calculate the GHG-emissions from palm oil production systems. Moreover, the internal nitrogen recycling on the plantation was calculated based on monitoring data in North Sumatra.

Results and discussion

A calculation methodology is detailed in Annex V of the EU-RED. Some important aspects necessary to calculate the GHG emission savings correctly are insufficiently considered, e.g.: ? “Nitrogen recycling” within the plantation due to fronds remaining on the plantation is ignored. The associated organic N-input to the plantation and the resulting nitrous oxide emissions is not considered within the calculations, despite crop residues being taken into account for annual crops in the BIOGRACE tool. ? The calculation of GHG-emissions from residue and waste water treatment is inappropriately implemented despite being a hot-spot for GHG emissions within the life cycle of palm oil and palm oil biodiesel. Additionally, no distinction is made between palm oil and palm kernel oil even though palm kernel oil is rarely used for biodiesel production. ? The allocation procedure does not address the most relevant oil mill management practices. Palm oil mills produce crude palm oil (CPO) in addition either nuts or palm kernels and nut shells. In the first case, the nuts would be treated as co-products and upstream emissions would be allocated based on the energy content; in the second case the kernels would be treated as co-products while the shelöls are considered as waste without upstream emissions. This has a significant impact on the resulst or GHG savings, respectively. ? It is not specified whether indirect GHG emissions from nitrogen oxide emission from the heat and power unit of palm oil mills should be taken into account.

Conclusions and recommendations

In conclusion, the existing calculation methodology described in Annex V of the EU-RED and default values are insufficient for calculating the real GHG emission savings from palm oil and palm oil biodiesel. The current default values do not reflect relevant management practices. Additionally, they protect poor management practices, such as the disposal of empty fruit bunches (EFB), and lead to an overestimation of GHG savings from palm oil biodiesel. A default value for EFB disposal must be introduced because resulting GHG emissions are substantial. Organic nitrogen from fronds must be taken into account when calculating real GHG savings from palm oil biodiesel. Further, more conservative data for FFB yield and fugitive emissions from wastewater treatment should be introduced in order to foster environmental friendly management options. Moreover, credits for bioenergy production from crop residues should be allowed in order to foster the mobilization of currently unused biomass.     

A comparison of the GHG emissions caused by manufacturing tissue paper from virgin pulp or recycled waste paper

Purpose

The aim of this work is to compare greenhouse gas (GHG) emissions from producing tissue paper from virgin pulp (VP) or recycled waste paper (RWP). In doing so, the study aims to inform decision makers at both company and national levels which are the main causes of emissions and to suggest the actions required to reduce pollution.

Methods

An attributional life cycle assessment (LCA) was performed in order to estimate and compare the GHG emissions of the two processes. LCA allows us to assess how the choice of raw material for VP and RWP processes influences total GHG emissions of tissue paper production, what are the main drivers behind these emissions and how do the direct materials; energy requirements and transportation contribute to the generation of emissions. The cradle-to-gate approach is carried out.

Results and discussion

The results show that demands for both thermal energy and electricity are higher for the RWP than for the VP if only the manufacturing stages are considered. However, a different picture emerges when the analysis looks at the entire life cycle of the production. GHG from the VP are about 30 % higher than the RWP, over the life cycle emitting 568 kg CO₂ eq more per kilogram of tissue paper. GHG emissions from the wood pulping alone were 559 g CO₂ eq per kilogram of tissue paper, three times higher than waste paper collection and transportation.

Conclusions

In terms of GHG emissions from cradle to gate, the recycled process less intensive than the virgin one for two reasons. First, as shown in the results the total GHG emissions from RWP are lower than those from VP due to relatively lower energy and material requirements. Second is the non-recyclability nature of tissue paper. Because the tissue paper is the last use of fibre, using RWP as an input would be preferable over using VP. The environmental profile of the tissue products both from RWP and VP can be improved if the following conditions are considered by the company. First, the company should consider implementing a cogeneration unit to simultaneously generate both useful heat and electricity. Second, it may consider changing the VP mix, in order to avoid the emissions associated with long distance transpiration effort. Third, there is the option of using sludge as fuel, which would reduce the total fossil fuel requirement.     

Life cycle assessment of commodity chemical production from forest residue via fast pyrolysis

Purpose

This life cycle assessment evaluates and quantifies the environmental impacts of renewable chemical production from forest residue via fast pyrolysis with hydrotreating/fluidized catalytic cracking (FCC) pathway.

Methods

The assessment input data are taken from Aspen Plus and greenhouse gases, regulated emissions, and energy use in transportation (GREET) model. The SimaPro 7.3 software is employed to evaluate the environmental impacts.

Results and discussion

The results indicate that the net fossil energy input is 34.8 MJ to produce 1 kg of chemicals, and the net global warming potential (GWP) is ?0.53 kg CO₂ eq. per kg chemicals produced under the proposed chemical production pathway. Sensitivity analysis indicates that bio-oil yields and chemical yields play the most important roles in the greenhouse gas footprints.

Conclusions

Fossil energy consumption and greenhouse gas (GHG) emissions can be reduced if commodity chemicals are produced via forest residue fast pyrolysis with hydrotreating/FCC pathway in place of conventional petroleum-based production pathways.     

PET bottle reverse logistics—environmental performance of California’s CRV program

Purpose

Disposable beverage bottles made of polyethylene terephthalate (PET) stand in sharp contrast to many other disposable plastic packaging systems in the US for their high level of post-consumer recovery for recycling. This is due in part to container deposit programs in several US states, such as the California Redemption Value (CRV) program. We investigate the impacts of PET bottle recycling in the CRV program to evaluate its effectiveness at reducing environmental burdens.

Methods

We develop a life cycle model using standard process LCA techniques. We use the US LCI database to describe the energy production infrastructure and the production of primary materials. We describe the inventory and logistical requirements for materials recovery on the basis of state-maintained statistics and interviews with operators and industry representatives. We report inventory indicators describing energy, freight, and waste disposal requirements. We report several impact indicators based on CML and TRACI-2.0 techniques. We apply system expansion to compare post-consumer activities to produce secondary polymer against equivalent primary production.

Results and discussion

While bottle collection is distributed across the state, processing is more centralized and occurs primarily near urban centers. The average distance traveled by a bottle from discard to recovery is 145–175 km. Recycling requires 0.45–0.66 MJ of primary energy/L of beverage, versus 3.96 MJ during the pre-consumer phase. Post-consumer environmental impacts are significantly lower than pre-consumer impacts, with the exception of eutrophication. The results are robust to model sensitivity, with allocation of fuel for bottle collection being the most significant parameter. Curbside collection is slightly more energy efficient than consumer drop-off, and is subject to smaller parametric uncertainty. Recycling has the potential for net environmental benefits in five of seven impact categories, the exceptions being smog (marginal benefits) and eutrophication (increased impacts).

Conclusions

California’s decentralized program for collecting and processing PET bottles has produced a system which generates a large stream of post-consumer material with minimal environmental impact. The selection of a reclamation locale is the most significant factor influencing post-consumer impacts. If secondary PET displaces primary material, several environmental burdens can be reduced.

Recommendations and perspectives

Our results suggest that deposit programs on disposable packaging are an effective policy mechanism to increase material recovery and reduce environmental burdens. Deposit programs for other packaging systems should be considered.     

Cost-effectiveness of bioethanol policies to reduce carbon dioxide emissions in Greece

Purpose

The aim of this study was to evaluate the cost-effectiveness of bioethanol as regards to its carbon dioxide emissions. The production of the raw material accounts for more than 50 % of the total cost as well as having a significant part of greenhouse gases emitted during the entire process. For this reason, special emphasis is given to a change in agricultural land usage influenced by the demand of biofuel. Therefore, we have estimated the extent of policy influence according to its bioethanol cost-effectiveness. A case study on bioethanol production in an ex-sugar factory in the region of Thessaly, Greece, illustrates the above ideas.

Methods

A partial equilibrium micro-economic model of regional supply in the arable farming system of Thessaly was coupled to industrial processing sub-models of bioethanol production from beets and grains. The maximisation of total welfare determines the most suitable crop mix for farmers as well as the lowest cost configurations for industry and, eventually, the minimal level of support by the government for biofuel activity to take off. The environmental performance is assessed under the life cycle assessment (LCA) framework following three interrelated phases: data inventory, data analysis and interpretation. The economic burden to society to support the activity divided by avoided CO₂ eq. emissions indicates the bioethanol cost-effectiveness, in other words, the cost of greenhouse gases emissions savings.

Results

The integrated agro-industry model has been parametrically run for a range of biofuel capacities. A change in direct land use results in lower emissions in the agricultural phase, since energy crops are a substitute for intensive cultivations, such as cotton and corn. A change in indirect land use moderates these estimations, as it takes in account imported food crops that are replaced by energy crops in the region. The savings in cost vary around 160 euros per ton of CO₂ eq. for the basic agricultural policy scenario. The current policy that supports cotton production by means of increased coupled area payment has increased up to 30 % the cost of greenhouse gas savings due to bioethanol production.

Conclusions

An integrated model, articulating the agricultural supply of biomass with ethanol processing, maximises the total surplus that is under constraints in order to determine the cost-effectiveness for different production levels. Results demonstrate that economic performances, as well as the environmental cost-effectiveness of bioethanol, are clearly affected by the parameters of agricultural policies. Therefore, bioenergy, environmental and economic performances, when based on LCA and the conceptual change in land usage, are context dependent. Agricultural policies for decoupling subsidies from production are in favour of cultivation in biomass for energy purposes.     

Environmental impacts of end-of-life vehicles’ management: recovery versus elimination

Purpose

In Portugal, the management of end-of-life vehicles (ELV) is set out in targets of the European Union policy for the year 2015, including 85 % recycling, 95 % recovery, and maximum of 5 % landfilling. These goals will be attained only through more efficient technologies for waste separation and recycling of shredder residues or higher rates of dismantling components. Focusing on this last alternative, a field experiment was carried out. There is potential for additional recycling/recovery of 10 %.

Methods

Three scenarios were proposed for the management of ELV wastes: (1) scenario 1 corresponds to the baseline and refers to the current management, i.e., the 10 % of ELV wastes are shredded whereby some ferrous and non-ferrous metals are recovered and the remaining fraction, called automotive shredder residues (ASR), is landfilled, (2) scenario 2 wherein the ASR fraction is incinerated with energy recovery, and (3) scenario 3 includes the additional dismantling of components for recycling and for energy recovery through solid recovered fuel, to be used as a fuel substitute in the cement industry. The environmental performance of these scenarios was quantified by using the life cycle assessment methodology. Five impact categories were assessed: abiotic resource depletion, climate change, photochemical oxidant creation, acidification, and eutrophication.

Results and discussion

Compared to the other scenarios, in scenario 1 no benefits for the impact categories of climate change and eutrophication were observed. Scenario 2 has environmental credits due to the recycling of ferrous and non-ferrous metals and benefits from energy recovery. However, this scenario has a significant impact on climate change due to emissions from thermal oxidation of polymeric materials present in the ASR fraction. A net environmental performance upgrading seems to be ensured by scenario 3, mainly due to replacing fossil fuel by solid recovered fuel.

Conclusions

The proposed additional dismantling of ELV (scenario 3) not only brings environmental benefits but also meets the European recovery and recycling targets. The associated increase of dismantling costs can be compensated by the additional recycling material revenues as well as social benefits by a rise in employment.     

Impacts of flexible pavement design and management decisions on life cycle energy consumption and carbon footprint

Purpose

The study aims to develop a methodological framework to estimate life cycle energy consumption and greenhouse gas (GHG) emissions related to pavement design and management decisions. Another objective is to apply the framework to the design and management of flexible highway pavement in Hong Kong. Traditionally, pavement design and management decisions are solely based on economic considerations. This study quantifies the relationships between such decisions and the environmental impacts, thereby helping highway agencies understand the environmental implications of their decisions and make more balanced decisions to improve highway sustainability.

Methods

(1) A methodological framework is developed by integrating the mechanistic-empirical pavement design guide (ME-PDG) and life cycle assessment (LCA) methods. (2) The calculation processes for the detailed components in the framework are proposed by synthesizing existing models, data, and tools. (3) In applying the framework to pavement design and management in Hong Kong, a large number of simulations are conducted to generate pavement performance data at different combinations of pavement thickness, roughness trigger value, and traffic levels. (4) GHG emissions and energy consumption are calculated for each simulation scenario, and the results are used to build statistical regression models. (5) The simulation and calculation results are also analyzed to gain additional insights on the environmental impacts of pavement design and management decisions.

Results and conclusions

(1) The developed framework that integrates ME-PDG and LCA methods is useful to assess pavement-related life cycle energy consumption and GHG emissions. (2) The developed regression models can well capture the trends of life cycle energy consumption and GHG emissions at different traffic levels, using asphalt concrete (AC) layer thickness and roughness trigger value as independent variables. (3) Material production, road use, and congestion due to road closure dominate pavement-related life cycle energy use and GHG emissions. (4) Optimum pavement thickness and international roughness index (IRI) trigger values exist, and they vary with traffic levels.

     

Reference and functional unit can change bioenergy pathway choices

Purpose

This study aims to compare the life cycle greenhouse gas (GHG) emissions of two cellulosic bioenergy pathways (i.e., bioethanol and bioelectricity) using different references and functional units. It also aims to address uncertainties associated with a comparative life cycle analysis (LCA) for the two bioenergy pathways.

Methods

We develop a stochastic, comparative life cycle GHG analysis model for a switchgrass-based bioenergy system. Life cycle GHG offsets of the biofuel and bioelectricity pathways for cellulosic bioenergy are compared. The reference system for bioethanol is the equivalent amount of gasoline to provide the same transportation utility (e.g., vehicle driving for certain distance) as bioethanol does. We use multiple reference systems for bioelectricity, including the average US grid, regional grid in the USA according to the North American Electric Reliability Corporation (NERC), and average coal-fired power generation, on the basis of providing the same transportation utility. The functional unit is one unit of energy content (MJ). GHG offsets of bioethanol and bioelectricity relative to reference systems are compared in both grams carbon dioxide equivalents per hectare of land per year (g CO₂-eq/ha-yr) and grams carbon dioxide equivalents per vehicle kilometer traveled (g CO₂-eq/km). For the latter, we include vehicle cycle to make the comparison meaningful. To address uncertainty and variability, we derive life cycle GHG emissions based on probability distributions of individual parameters representing various unit processes in the life cycle of bioenergy pathways.

Results and discussion

Our results show the choice of reference system and functional unit significantly changes the competition between switchgrass-based bioethanol and bioelectricity. In particular, our results show that the bioethanol pathway produces more life cycle GHG emissions than the bioelectricity pathway on a per unit energy content or a per unit area of crop land basis. However, the bioethanol pathway can offer more GHG offsets than the bioelectricity pathway on a per vehicle kilometer traveled basis when using bioethanol and bioelectricity for vehicle operation. Given the current energy mix of regional grids, bioethanol can potentially offset more GHG emissions than bioelectricity in all grid regions of the USA.

Conclusions

The reference and functional unit can change bioenergy pathway choices. The comparative LCA of bioenergy systems is most useful for decision support only when it is spatially explicit to address regional specifics and differences. The difference of GHG offsets from bioethanol and bioelectricity will change as the grid evolves. When the grids get cleaner over time, the favorability of bioethanol for GHG offsets increases.     

Life cycle assessment of potential energy uses for short rotation willow biomass in Sweden

Purpose

Two different bioenergy systems using willow chips as raw material has been assessed in detail applying life cycle assessment (LCA) methodology to compare its environmental profile with conventional alternatives based on fossil fuels and demonstrate the potential of this biomass as a lignocellulosic energy source.

Methods

Short rotation forest willow plantations dedicated to biomass chips production for energy purposes and located in Southern Sweden were considered as the agricultural case study. The bioenergy systems under assessment were based on the production and use of willow-based ethanol in a flexi fuel vehicle blended with gasoline (85 % ethanol by volume) and the direct combustion of willow chips in an industrial furnace in order to produce heat for end users. The standard framework for LCA from the International Standards Organisation was followed in this study. The environmental profiles as well as the hot spots all through the life cycles were identified.

Results and discussion

According to the results, Swedish willow biomass production is energetically efficient, and the destination of this biomass for energy purposes (independently the sort of energy) presents environmental benefits, specifically in terms of avoided greenhouse gases emissions and fossil fuels depletion. Several processes from the agricultural activities were identified as hot spots, and special considerations should be paid on them due to their contribution to the environmental impact categories under analysis. This was the case for the production and use of the nitrogen-based fertilizer, as well as the diesel used in agricultural machineries.

Conclusions

Special attention should be paid on diffuse emissions from the ethanol production plant as well as on the control system of the combustion emissions from the boiler.     

Life cycle greenhouse gas emissions of palm oil production by wet and dry extraction processes in Thailand

Purpose

The crude palm oil (CPO) extraction is normally done by a wet extraction process, and wastewater treatment of the wet process emits high levels of greenhouse gases (GHGs). A dry process extracts mixed palm oil (MPO) from palm fruit without using water and has no GHG emissions from wastewater treatment. This work is aimed at determining the GHG emissions of a dry process and at evaluating GHG savings on changing from wet to dry process, including land use change (LUC) effects.

Methods

Life cycle assessment from cradle to gate was used. The raw material is palm fruits. The dry process includes primary production, oil room, and utilities. MPO is the main product, while palm cake and fine palm residue are co-products sold for animal feed. Case studies were undertaken without and with carbon stocks of firewood and of nitrogen recycling at plantations from fronds. Allocations by mass, economic, and heating values were conducted. The trading of GHG emissions from co-products to GHG emissions from animal feed was assessed. The GHG emissions or savings from direct LUC (dLUC) and from indirect LUC (iLUC) effects and for the change from wet to dry process were determined.

Results and discussion

Palm fruit and firewood were the major GHG emission sources. Nitrogen recycling on plantations from fronds significantly affects the GHG emissions. With the carbon stocks, the GHG emissions allocated by energy value were 550 kg CO₂ eq/t MPO. The GHG emissions were affected by ?3 to 37% for the change from wet to dry process. When the plantation area was increased by 1 ha and the palm oil extraction was changed from wet to dry process, and the change included dLUC and iLUC, the GHG savings ranged from ?0.94 to 5.08 t CO₂ eq/ha year. The iLUC was the main GHG emission source. The GHG saving mostly originated from the change of extraction process and from the dLUC effect. Based on the potential use of biodiesel production from oil palm, during 2015–2036 in Thailand, when the extraction process was changed and dLUC and iLUC effects were included, the saving in GHG emissions was estimated to range from ?35,454 to 274,774 t CO₂ eq/year.

Conclusions

The change of palm oil extraction process and the LUC effects could minimize the GHG emissions from the palm oil industry. This advantage encourages developing policies that support the dry extraction process and contribute to sustainable developments in palm oil production.

     

Life cycle assessment of non-traditional treatments for the valorisation of dry soils in earthworks

Purpose

Sustainable development principles are leading earthwork companies to use all-natural materials extracted from the construction site to build the infrastructure. Natural materials with low characteristics must be improved. For dry soils, the common solution is to increase the compaction energy or add important quantities of water to reach the target dry density and bearing capacity. To reduce the environmental impact of their activities, the use of industrial organic products has been proposed. The aim of this study was to assess the potential benefits that could be expected from the use of these non-traditional treatments in earthworks with a well-recognised environmental impact assessment methodology.

Methods

Three non-traditional products were selected as follows: an acid solution (AS), an enzymatic solution (ES) and a calcium lignosulfonate (LS). For each of these categories, geotechnical properties such as compaction, bearing capacity, unconfined compressive strength and stiffness were first determined. Based on these results, the construction strategy for which non-traditional additives lead to greater improvement of soil properties was defined. The environmental balance of each option was then determined via a comparative process life cycle assessment study that considered ten impact categories.

Results and discussion

An experimental study showed the ability of enzymatic and lignosulfonate additives to improve soil characteristics with significant savings of water at the construction stage. The purpose of the study was also to compare the global environmental impact of each treatment strategy defined from laboratory investigations. The life cycle assessment results showed that some construction strategies lead to a significant reduction in the environmental impact compared with the reference strategy. However, these environmental improvements are strongly linked to the choice of the construction strategy and site conditions as discussed in the sensitivity analysis.

Conclusions

Within the three tested non-traditional additives, enzymatic and lignosulfonate treatments showed an association of technical and environmental interest for the compaction of dry soils. As demonstrated in the sensitivity analysis, these benefits are achieved when the production and transport steps have limited environmental impact. Thus, despite an important transportation distance for enzymatic additive, the small quantities that must be used (0.002 % by dry weight) have a limited contribution on the global environmental impact. In contrast, the production step strongly impacts the treatment with lignosulfonates. Moreover, environmental interest remains strongly dependent on the site conditions and construction strategy, which is why the adopted methodology can accurately perform an initial evaluation before implementing a soil treatment with a non-traditional product.

     

Comparative LCA of multi-product processes with non-common products: a systematic approach applied to chlorine electrolysis technologies

Purpose

Multi-product processes are one source of multi-functionality causing widely discussed methodological problems within life cycle assessment. A multi-functionality problem exists for comparative life cycle assessment (LCA) of multi-product processes with non-common products. This work develops a systematic workflow for fixing the multi-functionality problem caused by the non-common products. A novel technology for chlor-alkali electrolysis is analyzed and compared to the industrial standard technology to illustrate the approach and to benchmark the new technology's environmental impact.

Methods

A matrix-based workflow for comparative LCA of multi-product systems is presented. Products are distinguished in main products and by-products based on the reason of process operation. We argue that only main products form the reference flows of the compared multi-product systems. Fixing the multi-functionality problem follows directly from the chosen reference flows. The framework suggests system expansion to fix the multi-functionality problem if non-common main products exist. Non-common by-products still cause a multi-functionality problem. These by-products are systematically identified and the multi-functionality problem is fixed with avoided burden and allocation. A case study applies the workflow for comparing environmental impacts of the standard chlorine electrolysis to a novel process using oxygen-depolarized cathodes. Three scenarios are derived and evaluated. The assessed impact categories are cumulative energy demand, global warming potential, acidification potential, photochemical ozone creation potential, eutrophication potential, and human toxicity potential.

Results and discussion

The proposed workflow minimizes the methodological choices. The multi-functionality problem is systematically fixed based on the distinction between the main products and by-products. Inconsistent solutions are prevented by rigorous identification of unequal by-products within the compared systems. Selecting avoided burden processes or allocation factors is the remaining ambiguous choice common to the standard methods. The case study demonstrates the applicability of the workflow to comparative LCA of multi-product systems. The case study results show lower environmental impacts for the novel electrolysis technology in all practically relevant scenarios and impact categories.

Conclusions

The framework for comparative LCA of multi-product systems with non-common products adds systematic clarity to the general ISO standards. The approach reduces the subjective choices of LCA practitioners to the identification of reason of process operation. This reason is defined if the site-specific economic conditions are known. The matrix-based formulation allows identification of inconsistencies caused by multi-functionality. For the novel electrolysis technology, the results indicate significant potential for environmental impact reduction.