Comparative Life Cycle Assessment of Charcoal,Biogas, and Liquefied Petroleum Gas as Cooking Fuels in Ghana

Standard life cycle assessment (LCA) methodology has been used to determine and compare the environmental impacts of three different cooking fuels used in Ghana, namely, charcoal, biogas, and liquefied petroleum gas (LPG). A national policy on the use of cooking fuels would have to look at the environmental, social, and cost implications associated with the fuel types. This study looked at the environmental aspect of using these fuels. The results showed that global warming and human toxicity were the most significant overall environmental impacts associated with them, and charcoal and LPG, respectively, made the largest contribution to these impact categories. LPG, however, gave relatively higher impacts in three other categories of lesser significance—that is, eutrophication, freshwater aquatic ecotoxicity, and terrestrial ecotoxicity potentials. Direct comparison of the results showed that biogas had the lowest impact in five out of the seven categories investigated. Charcoal and LPG had only one lowest score each. From the global warming point of view, however, LPG had a slight overall advantage over the others, and it was also the most favorable at the cooking stage, in terms of its effect on humans.     

A Theoretical Foundation for Life-Cycle Assessment

The presence of value judgments in life-cycle impact assessment (LCIA) has been a constant source of controversy. According to a common interpretation, the international standard on LCIA requires that the assessment methods used in published comparisons be "value free." Epistemologists argue that even natural science rests on "constitutive" and "contextual" value judgments. The example of the equivalency potential for climate change, the global warming potential (GWP), demonstrates that any impact assessment method inevitably contains not only constitutive and contextual values, but also preference values. Hence, neither life-cycle assessment (LCA) as a whole nor any of its steps can be "value free." As a result, we suggest a more comprehensive definition of objectivity in LCA that allows arguments about values and their relationship to facts. We distinguish three types of truth claims: factual claims, which are based on natural science; normative claims, which refer to preference values; and relational claims, which address the proper relation between factual knowledge and values. Every assessment method, even the GWP, requires each type of claim. Rational arguments can be made about each type of claim. Factual truth claims can be assessed using the scientific method. Normative claims can be based on ethical arguments. The values of individuals or groups can be elicited using various social science methods. Relational claims must follow the rules of logic. Relational claims are most important for the development of impact assessment methods. Because LCAs are conducted to satisfy the need of decision makers to consider environmental impacts, relational claims about impact assessment methods should refer to this goal. This article introduces conditions that affect environmental decision making and discusses how LCA—values and all—can be defended as a rational response to the challenge of moving uncertain scientific information into the policy arena.     

Life Cycle Assessment of Biosolids Land Application and Evaluation of the Factors Impacting Human Toxicity through Plant Uptake

Due to increasing environmental concerns in the wastewater treatment sector, the environmental impacts of organic waste disposal procedures require careful evaluation. However, the impacts related to the return of organic matter to agricultural soils are difficult to assess. The goals of this study are to assess the environmental impacts of land application of two types of biosolids (dried and composted, respectively) from the same wastewater treatment plant in France, and to improve the quantification of human toxicity. A life cycle assessment (LCA) was carried out on a case study based on validated data from an actual wastewater treatment plant. Numerous impacts were included in this analysis, but a particular emphasis was laid on human toxicity via plant ingestion. For six out of the eight impact categories included in the analysis, the dried biosolids system was more harmful to the environment than the composting route, especially regarding the consumption of primary energy. Only human toxicity via water, soil, and air compartments and ozone depletion impacts were higher with the composted biosolids.     

Using Life-Cycle Assessment in Process Design

This article presents the application of life-cycle assessment in early phases of process design in the context of technology that employs a bio-based material. The goal is to identify hot spots in the process chains with regard to environmental impacts by performing a dominance analysis. By focusing his activities on the hot spots identified, the designer is given the opportunity to efficiently improve environmental performance. This approach is illustrated for the case of supercritical water gasification, a novel technology for the treatment of organic feedstock with high moisture content. In the reactor under supercritical conditions, organic components are converted into a high-caloric synthesis gas, with hydrogen, methane, and carbon dioxide as the main products. The data used for the assessment are obtained from laboratory tests and the literature, completed by assumptions for missing data. The scope of assessment ranges from the extraction of raw materials to the product, that is, hydrogen (cradle to gate) with sewage sludge of a municipal wastewater treatment plant used as feedstock. The assessment identifies the main sources of environmental impacts. The predominant process step in terms of global warming potential is the supply of the gasification process with additional heat. The production of a blending agent in the dewatering step is the main source of the impact category of acidification, whereas the wastewater treatment plant is the origin of emissions that lead to eutrophication. The revealed sources are analyzed further and options for reducing the environmental impacts are discussed.     

Critical review of the influences of nanoparticles on biological wastewater treatment and sludge digestion

Nanoparticles (NPs), with at least one dimension less than 100?nm, are substantially employed in consumer and industrial products due to their specific physical and chemical properties. The wide uses of engineered NPs inevitably cause their release into the environment, especially wastewater treatment plants. Therefore, it is essential to systematically assess their potential impact on biological wastewater treatment and subsequent sewage sludge digestion. This review aims to provide such support. First, this paper reviews the recent advances on the analytical developments and nano–bio interface of NPs in wastewater and sewage sludge treatment. The effects of NPs on biological wastewater treatment and sewage sludge digestion and related mechanisms are discussed in detail. Finally, the key questions that need to be answered in the future are pointed out, which include on-line revelation of the changes of NPs in sewage and sludge environments, in situ assessment of the variations of microorganisms involved in these biological systems after they are exposed to NPs. Differentiation of the contribution of individual toxicity mechanisms to these systems, and the identification of under what conditions the nanoparticle-induced toxicity will be increased or decreased are also considered.     

Beyond Global Warming Potential: A Comparative Application of Climate Impact Metrics for the Life Cycle Assessment of Coal and Natural Gas Based Electricity

In the ongoing debate about the climate benefits of fuel switching from coal to natural gas for power generation, the metrics used to model climate impacts may be important. In this article, we evaluate the life cycle greenhouse gas emissions of coal and natural gas used in new, advanced power plants using a broad set of available climate metrics in order to test for the robustness of results. Climate metrics included in the article are global warming potential, global temperature change potential, technology warming potential, and cumulative radiative forcing. We also used the Model for the Assessment of Greenhouse‐gas Induced Climate Change (MAGICC) climate‐change model to validate the results. We find that all climate metrics suggest a natural gas combined cycle plant offers life cycle climate benefits over 100 years compared to a pulverized coal plant, even if the life cycle methane leakage rate for natural gas reaches 5%. Over shorter time frames (i.e., 20 years), plants using natural gas with a 4% leakage rate have similar climate impacts as those using coal, but are no worse than coal. If carbon capture and sequestration becomes available for both types of power plants, natural gas still offers climate benefits over coal as long as the life cycle methane leakage rate remains below 2%. These results are consistent across climate metrics and the MAGICC model over a 100‐year time frame. Although it is not clear whether any of these metrics are better than the others, the choice of metric can inform decisions based on different societal values. For example, whereas annual temperature change reported may be a more relevant metric to evaluate the human health effects of increased heat, the cumulative temperature change may be more relevant to evaluate climate impacts, such as sea‐level rise, that will result from the cumulative warming.     

Short- and long-term greenhouse gas and radiative forcing impacts of changing water management in Asian rice paddies

Fertilized rice paddy soils emit methane while flooded, emit nitrous oxide during flooding and draining transitions, and can be a source or sink of carbon dioxide. Changing water management of rice paddies can affect net emissions of all three of these greenhouse gases. We used denitrification–decomposition (DNDC), a process‐based biogeochemistry model, to evaluate the annual emissions of CH₄, N₂O, and CO₂ for continuously flooded, single‐, double‐, and triple‐cropped rice (three baseline scenarios), and in further simulations, the change in emissions with changing water management to midseason draining of the paddies, and to alternating crops of midseason drained rice and upland crops (two alternatives for each baseline scenario). We used a set of first‐order atmospheric models to track the atmospheric burden of each gas over 500 years. We evaluated the dynamics of the radiative forcing due to the changes in emissions of CH₄, N₂O, and CO₂ (alternative minus baseline), and compared these with standard calculations of CO₂‐equivalent emissions using global warming potentials (GWPs). All alternative scenarios had lower CH₄ emissions and higher N₂O emissions than their corresponding baseline cases, and all but one sequestered carbon in the soil more slowly. Because of differences in emissions, in radiative forcing per molecule, and in atmospheric time constants (lifetimes), the relative radiative impacts of CH₄, N₂O, and CO₂ varied over the 500‐year simulations. In three of the six cases, the initial change in radiative forcing was dominated by reduced CH₄ emissions (i.e. a cooling for the first few decades); in five of the six cases, the long‐term radiative forcing was dominated by increased N₂O emissions (i.e. a warming over several centuries). The overall complexity of the radiative forcing response to changing water management could not easily be captured with conventional GWP calculations.     

土地利用方式转变后灰色森林土有机碳矿化的温度响应特征

通过室内培育试验,分析了土地利用方式转变后灰色森林土有机碳矿化过程及其对温度变化的响应特征.结果表明：原始林转变为农田后,0～10 cm、10～20 cm的土壤有机碳和全氮含量分别下降了68.5%、76.8%和40.5%、44.4%;而农田土壤有机碳的平均矿化速率和累积矿化量仅分别为原始林的24.4%～43.2%和9.20％～13.7％.低温条件下（<25 ℃）土壤有机碳矿化的温度敏感性显著高于高温条件下（>25 ℃）.低温条件下（<25 ℃）两种利用方式的土壤有机碳矿化对温度变化的敏感性没有显著差异;但高温条件下（>25 ℃）,农田0～10 cm土壤有机碳矿化的温度敏感性高于原始林,而农田10～20 cm土壤有机碳矿化的温度敏感性明显较低.     

施用生物炭与硝化抑制剂对菜地综合温室效应的影响

采用静态暗箱-气相色谱法,研究施用生物炭与添加硝化抑制剂对菜地周年综合温室效应的影响.结果表明: 与不施用生物炭相比,施用生物炭处理N₂O和CH₄的综合温室效应增加8.7%~12.4%,蔬菜产量增加16.1%~52.5%,温室气体强度降低5.4%~28.7%.添加硝化抑制剂显著减少N₂O排放,不影响CH₄排放,综合温室效应减少17.5%~20.6%,蔬菜产量增加21.2%~40.1%,温室气体强度显著降低.混合施用生物炭与硝化抑制剂一方面增加蔬菜产量,另一方面显著增加综合温室效应(增幅为10.6%～11.2%).因此,在菜地添加硝化抑制剂,既能保证蔬菜产量又能减少温室气体排放,是合适的减排措施.     

Use of Symbiosis Products from Integrated Pulp and Paper and Carbon Steel Mills: Legal Status and Environmental Burdens

This study assesses the policy/legal status of both multistream residues and potential secondary products (“symbiosis products”) and whether there could be environmental benefits associated with the utilization of residues from integrated pulp and paper and carbon steel mills as raw materials for such secondary products. Waste‐related European Union (EU) and Finnish policy and legal instruments were reviewed to identify potential constraints for, and suggested next steps in, the development of potential process industry residue‐based symbiosis products. The products were soil amendment pellets, low‐grade concrete, and mine filler. A global warming potential (GWP) assessment and an exergy analysis were applied to these potential symbiosis products. Some indicative GWP calculations of greenhouse gas emissions associating similar and/or analogous products based on virgin primary raw materials, more energy‐intensive processes, and the alternative treatment of these residues as wastes are also presented. This study addresses GWP, exergy, and legal aspects in a holistic manner to determine the potential environmental benefits of secondary products within the EU legal framework. The GWP assessment and exergy analysis indicate that the utilization of multistream residues causes very low environmental burdens in terms of GWP. The utilization option can have potential environmental benefits in terms of GWP through process replacement and avoided landfilling and waste treatment impacts, as well as potentially through emission reductions from product replacement if suitable and safe applications can be identified. Waste regulation does not define the legal requirements under which utilizing residues in such novel concepts as introduced in this study would be possible, nor how waste status could be removed and product‐based legislation be applied to the potential products instead.     

Environmental Evaluation of Industry Cluster Strategies with a Life Cycle Perspective: Replacing Fossil Feedstock with Forest‐Based Feedstock and Increasing Thermal Energy Integration

Symbiotic linkages in industry clusters in the form of interconnected materials, energy and information flows, and close proximity provide unique opportunities to develop efficient environmental strategies. The purpose of our study is to examine the practical potential of applying a life cycle approach in strategy evaluations, as the environmental impact caused by industrial symbiosis systems outside the company gates has been scarcely addressed. This is done by evaluating two strategies for an industry cluster in Sweden: (1) to replace a share of the fossil feedstock used in the industry cluster with forest‐based feedstock and (2) to improve energy efficiency through thermal energy integration. The environmental impact reduction potential of the strategies is evaluated using life cycle assessment. The ratio between investment cost and reduced global warming potential is used as an indicator to evaluate the cost‐effectiveness of the strategies. Results demonstrate the importance of applying a life cycle perspective as the assessment outcome depends heavily on whether only on‐site consequences are assessed or if upstream and downstream processes are also included. 20% of the greenhouse gas emission reduction of the energy integration strategy occurs off‐site, whereas the forest strategy has the largest reduction potential off‐site, >80%.     

Greenhouse Gas Emissions Reduction Opportunities for Concrete Pavements

Concrete pavements are a vital part of the transportation infrastructure, comprising nearly 25% of the interstate network in the United States. With transportation authorities and industry organizations increasingly seeking out methods to reduce their carbon footprint, there is a need to identify and quantitatively evaluate the greenhouse gas (GHG) emission reduction opportunities that exist in the concrete pavement life cycle. A select few of these opportunities are explored in this article in order to represent possible reduction approaches and their associated cost‐effectiveness: reducing embodied emissions by increasing fly ash content and by avoiding overdesign; increasing albedo by using white aggregates; increasing carbonation by temporarily stockpiling recycled concrete aggregates; and reducing vehicle fuel consumption by adding an extra rehabilitation. These reduction strategies are evaluated for interstate, arterial, collector, and local road designs under urban and rural scenarios. The results indicate that significant GHG emission reductions are possible, with over half of the scenarios resulting in 10% reductions, compared to unimproved baseline designs. Given the right conditions, each scenario has the potential to reduce GHG emissions at costs comparable to the current price of carbon.     

Efficacy of Biosolids in Assisted Phytostabilization of Metalliferous Acidic Sandy Soils with Five Grass Species

The role of sewage sludge as an immobilising agent in the phytostabilization of metal-contaminated soil was evaluated using five grass species viz., Dactylis glomerata L., Festuca arundinacea Schreb., F. rubra L., Lolium perenne L., L. westerwoldicum L. The function of metal immobilization was investigated by monitoring pH, Eh and Cd, Pb, and Zn levels in column experiment over a period of 5-months. Grasses grown on sewage sludge-amendments produced high biomass in comparison to controls. A significant reduction in metal uptake by plants was also observed as a result of sewage sludge application, which was attributed to decreased bioavailability through soil stabilisation. We have observed that the sludge amendment decreased metal bioavailability and concentrations in soil at a depth of 25 cm, in contrast to untreated columns, where metal concentrations in the soil solution were very high.     

Effects of Sludge and pH Adjustment on Cd Speciation in Soil and Growth and Cd Accumulation in Pak Choi

The objective of this study was to assess the effects of soil pH adjustment and treatment with sludge on plant growth and cadmium (Cd) accumulation in Chinese cabbage (pak choi) grown in Cd-contaminated soils. Soil was artificially spiked to raise its final Cd concentration to 10 mg/kg, adjusted to different pH values, and then supplemented with 5% sludge: either biosolids (BS) from wastewater treatment or sludge from drinking water treatment (WTS). Pak choi seeds were sown and the seedlings potted in the treated soil, then grown in a greenhouse for 45 days. The added Cd was present mainly in the exchangeable fraction and its concentration correlated to Cd accumulation in the roots and shoots. Adjustment of pH and application of sludge affected the Cd concentration in different fractions. Addition of WTS and adjustment to pH 7.0 inhibited growth and Cd accumulation in the pak choi. Addition of BS increased the soil nutrient content and thus enhanced growth and Cd accumulation. If pak choi were the only form of vegetable intake, consumption of pak choi grown in the Cd-spiked soils used in this study would exceed the maximum acceptable intake (60 μg/day) proposed by the World Health Organization.     

Three Strategies to Overcome the Limitations of Life-Cycle Assessment

Many research efforts aim at an extension of life‐cycle assessment (LCA) in order to increase its spatial or temporal detail or to enlarge its scope. This is an important contribution to industrial ecology as a scientific discipline, but from the application viewpoint other options are available to obtain more detailed information, or to obtain information over a broader range of impacts in a life‐cycle perspective. This article discusses three different strategies to reach these aims: (1) extension of LCA—one consistent model; (2) use of a toolbox—separate models used in combination; and (3) hybrid analysis—combination of models with data flows between them. Extension of LCA offers the most consistent solution. Developments in LCA are moving toward greater spatial detail and temporal resolution and the inclusion of social issues. Creating a supertool with too many data and resource requirements is, however, a risk. Moreover, a number of social issues are not easily modeled in relation to a functional unit. The development of a toolbox offers the most flexibility regarding spatial and temporal information and regarding the inclusion of other types of impacts. The rigid structure of LCA no longer sets limits; every aspect can be dealt with according to the logic of the relevant tool. The results lack consistency, however, preventing further formal integration. The third strategy, hybrid analysis, takes up an intermediate position between the other two. This strategy is more flexible than extension of LCA and more consistent than a toolbox. Hybrid analysis thus has the potential to combine the strong points of the other two strategies. It offers an interesting path for further discovery, broader than the already well‐known combination of process‐LCA and input‐output‐LCA. We present a number of examples of hybrid analysis to illustrate the potentials of this strategy. Developments in the field of a toolbox or of hybrid analysis may become fully consistent with LCA, and then in fact become part of the first solution, extension of LCA.     

A Carbon Footprint of Textile Recycling: A Case Study in Sweden

Global population growth and rising living standards are increasing apparel consumption. Consequently, consumption of resources and generation of textile waste are increasing. According to the Swedish Environmental Protection Agency, textile consumption increased by 40% between the years 2000 and 2009 in Sweden. Given that there is currently no textile recycling plant in Sweden, the aim of this article is to explore the potential environmental benefits of various textile recycling techniques and thereby direct textile waste management strategies toward more sustainable options. Three different recycling techniques for a model waste consisting of 50% cotton and 50% polyester were identified and a life cycle assessment (LCA) was made to assess the environmental performance of them. The recycling processes are: material reuse of textile waste of adequate quality; separation of cellulose from polyester using N‐methylmorpholine‐N‐oxide as a solvent; and chemical recycling of polyester. These are compared to incineration, representing conventional textile waste treatment in Sweden. The results show that incineration has the highest global warming potential and primary energy usage. The material reuse process exhibits the best performance of the studied systems, with savings of 8 tonnes of carbon dioxide equivalents (CO₂‐eq) and 164 gigajoules (GJ) of primary energy per tonne of textile waste. Sensitivity analyses showed that results are particularly sensitive to the considered yields of the processes and to the choice of replaced products. An integration of these recycling technologies for optimal usage of their different features for treatment of 1 tonne of textile waste shows that 10 tonnes CO₂‐eq and 169 GJ of primary energy could be saved.     

Bottom-Up Life-Cycle:Assessment of Product Consumption in Belgium

The present study shows the results and methodology applied to the study of the identification of priority product categories for Belgian product and environmental policy. The main goal of the study was to gather insight into the consumption of products in Belgium and their related life-cycle environmental impacts. The conclusions of this project on the product categories with major environmental contributions can be used to start up working groups involving stakeholders and initiate detailed product studies on the impact reduction potential that could be achieved by means of implementing product policy measures. Several ways of assessing product category environmental impacts and the effects of policy measures have been developed; 'bottom-up' or 'market-life-cycle assessment' is one of these, and we tried this approach for the situation in Belgium. Simplified life-cycle assessment (LCA) studies were conducted for representative average products within each function-based product category and the results were multiplied with market statistics. Using this approach, we found that building construction, building occupancy, and personal transport are among the major categories for Belgium. The major drawbacks of this approach are the system-level limitations and the existence of a broad spectrum of nonharmonized methods and datasets from which a sound preliminary selection had to be made. Consequently, the retrieval and selection of data was very time consuming and due to this we had to accept some major limitations in the study design. Nevertheless, the study has contributed to the development of a methodology for market-LCA and elements that can be picked up in currently ongoing and future work. The study concludes that to improve the feasibility and acceptance of this type of study there is a need for the development of a harmonized methodology on market-LCA, policy-relevant impact indicators as well as a harmonized and stakeholder-agreed-upon LCA databases.     

A Systems Approach to Sustainable Technical Product Design

Many existing methods for sustainable technical product design focus on environmental efficiency while lacking a framework for a holistic, sustainable design approach that includes combined social, technical, economic, and environmental aspects in the whole product life cycle, and that provides guidance on a technical product development level. This research proposes a framework for sustainable technical product design in the case of skis. We developed a ski under the Grown brand, benchmarked according to social, environmental, economic, and technical targets, following an initial sustainability assessment, and delivered the first environmental life cycle assessment (ELCA) and the first social life cycle assessment (SLCA) of skis. The framework applies a virtual development process as a combination of ELCA to calculate the environmental footprint as carbon equivalents of all materials and processes and a technical computer‐aided design (CAD) and computer‐aided engineering (CAE) simulation and virtual optimization using parameter studies for the nearly prototype‐free development of the benchmarked skis. The feedback loops between life cycle assessment (LCA) and virtual simulation led to the elimination of highly energy intensive materials, to the pioneering use of basalt fibers in skis, to the optimization of the use of natural materials using protective coatings from natural resins, and to the optimization of the production process. From an environmental perspective, a minimum 32% reduction in carbon equivalent emissions of materials in relation to other comparably performing skis has been achieved, as well as a pioneering step forward toward transparent communication of the environmental performance by the individual, comparable, and first published ski carbon footprint per volume unit.