LCA of a biorefinery concept producing bioethanol,bioenergy, and chemicals from switchgrass

Background, aim, and scope  

The availability of fossil resources is predicted to decrease in the near future: they are a non-renewable source, they cause environmental concerns, and they are subjected to price instability. Utilization of biomass as raw material in a biorefinery is a promising alternative to fossil resources for production of energy carriers and chemicals, as well as for mitigating climate change and enhancing energy security. This paper focuses on a biorefinery concept which produces bioethanol, bioenergy, and biochemicals from switchgrass, a lignocellulosic crop. Results are compared with a fossil reference system producing the same products/services from fossil sources.     

Airtight storage of moist wheat grain improves bioethanol yields

Background  

Drying is currently the most frequently used conservation method for cereal grain, which in temperate climates consumes a major part of process energy. Airtight storage of moist feed grain using the biocontrol yeast Pichia anomala as biopreservation agent can substantially reduce the process energy for grain storage. In this study we tested the potential of moist stored grain for bioethanol production.     

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.     

Techno-economics of integrating bioethanol production from spent sulfite liquor for reduction of greenhouse gas emissions from sulfite pulping mills

Background

Flow sheet options for integrating ethanol production from spent sulfite liquor (SSL) into the acid-based sulfite pulping process at the Sappi Saiccor mill (Umkomaas, South Africa) were investigated, including options for generation of thermal and electrical energy from onsite bio-wastes, such as bark. Processes were simulated with Aspen Plus® for mass- and energy-balances, followed by an estimation of the economic viability and environmental impacts. Various concentration levels of the total dissolved solids in magnesium oxide-based SSL, which currently fuels a recovery boiler, prior to fermentation was considered, together with return of the fermentation residues (distillation bottoms) to the recovery boiler after ethanol separation. The generation of renewable thermal and electrical energy from onsite bio-wastes were also included in the energy balance of the combined pulping-ethanol process, in order to partially replace coal consumption. The bio-energy supplementations included the combustion of bark for heat and electricity generation and the bio-digestion of the calcium oxide SSL to produce methane as additional energy source.

Results

Ethanol production from SSL at the highest substrate concentration was the most economically feasible when coal was used for process energy. However this solution did not provide any savings in greenhouse gas (GHG) emissions for the concentration-fermentation-distillation process. Maximizing the use of renewable energy sources to partially replace coal consumption yielded a satisfactory economic performance, with a minimum ethanol selling price of 0.83 US$/l , and a drastic reduction in the overall greenhouse gas emissions for the entire facility.

Conclusion

High substrate concentrations and conventional distillation should be used when considering integrating ethanol production at sulfite pulping mills. Bio-wastes generated onsite should be utilized at their maximum potential for energy generation in order to maximize the GHG emissions reduction.

     

Life cycle assessment of energy and GHG emissions during ethanol production from grass straws using various pretreatment processes

Purpose  

The aim of this study was to perform a well-to-pump life cycle assessment (LCA) to investigate the overall net energy balance and environmental impact of bioethanol production using Tall Fescue grass straw as feedstock. The energy requirements and greenhouse gas (GHG) emissions were compared to those of gasoline to explore the potential of bioethanol as sustainable fuel.     

An ecoprofile of thermoplastic protein derived from blood meal Part 2: thermoplastic processing

Purpose  

The purpose of this research was to develop a nonrenewable energy and greenhouse gas emissions ecoprofile of thermoplastic protein derived from blood meal (Novatein thermoplastic protein; NTP). This was intended for comparison with other bioplastics as well as identification of hot spots in its cradle-to-gate production. In Part 1 of this study, the effect of allocation on the blood meal used as a raw material was discussed. The objective of Part 2 was to assess the ecoprofile of the thermoplastic conversion process and to compare the cradle-to-gate portion of the polymer's life cycle to other bioplastics.     

Life cycle energy consumption and CO2 emission of an office building in China

Purpose  

Building is one of the main factors of energy use and greenhouse gas emissions. Reducing energy consumption and carbon dioxide (CO₂) emission from building is urgent for environmental protection and sustainable development. The objective of this study is to develop a life cycle assessment (LCA) model for an office building in China to assess its energy consumption and CO₂ emission, determine the whole life cycle phases, and the significant environmental aspects that contribute most to the impact.     

Diversity of lactic acid bacteria of the bioethanol process

Background  

Bacteria may compete with yeast for nutrients during bioethanol production process, potentially causing economic losses. This is the first study aiming at the quantification and identification of Lactic Acid Bacteria (LAB) present in the bioethanol industrial processes in different distilleries of Brazil.     

The impacts of deacetylation prior to dilute acid pretreatment on the bioethanol process

Background

There is currently considerable interest in developing renewable sources of energy. One strategy is the biological conversion of plant biomass to liquid transportation fuel. Several technical hurdles impinge upon the economic feasibility of this strategy, including the development of energy crops amenable to facile deconstruction. Reliable assays to characterize feedstock quality are needed to measure the effects of pre-treatment and processing and of the plant and microbial genetic diversity that influence bioconversion efficiency.

Results

We used the anaerobic bacterium Clostridium phytofermentans to develop a robust assay for biomass digestibility and conversion to biofuels. The assay utilizes the ability of the microbe to convert biomass directly into ethanol with little or no pre-treatment. Plant samples were added to an anaerobic minimal medium and inoculated with C. phytofermentans, incubated for 3 days, after which the culture supernatant was analyzed for ethanol concentration. The assay detected significant differences in the supernatant ethanol from wild-type sorghum compared with brown midrib sorghum mutants previously shown to be highly digestible. Compositional analysis of the biomass before and after inoculation suggested that differences in xylan metabolism were partly responsible for the differences in ethanol yields. Additionally, we characterized the natural genetic variation for conversion efficiency in Brachypodium distachyon and shrub willow (Salix spp.).

Conclusion

Our results agree with those from previous studies of lignin mutants using enzymatic saccharification-based approaches. However, the use of C. phytofermentans takes into consideration specific organismal interactions, which will be crucial for simultaneous saccharification fermentation or consolidated bioprocessing. The ability to detect such phenotypic variation facilitates the genetic analysis of mechanisms underlying plant feedstock quality.     

A spatially explicit whole-system model of the lignocellulosic bioethanol supply chain: an assessment of decentralised processing potential

Background  

Lignocellulosic bioethanol technologies exhibit significant capacity for performance improvement across the supply chain through the development of high-yielding energy crops, integrated pretreatment, hydrolysis and fermentation technologies and the application of dedicated ethanol pipelines. The impact of such developments on cost-optimal plant location, scale and process composition within multiple plant infrastructures is poorly understood. A combined production and logistics model has been developed to investigate cost-optimal system configurations for a range of technological, system scale, biomass supply and ethanol demand distribution scenarios specific to European agricultural land and population densities.     

Development of a new tank-to-wheels methodology for energy use and green house gas emissions analysis based on vehicle fleet modeling

Background, aim and scope  

Tank-to-Wheels (TtW) makes the largest contribution to the total Well-to-Wheels (WtW) energy consumption and greenhouse gas (GHG) emissions from fossil-derived transportation fuels. The most commonly adopted TtW methodologies to obtain vehicle energy consumption, energy efficiency, and GHG emissions used to date all have significant limitations. A new TtW methodology, which combines micro-scale virtual vehicle simulation with macro-scale fleet modeling, is proposed in this paper. The models capabilities are demonstrated using a case study based on data from the passenger car sector in Great Britain.     

The climate change implications of offshoring Finnish pulp production to South America

Purpose  

Offshoring of pulpwood production outside Europe is more and more common, which increases transport distances and also changes production technologies, raw material supply and energy production profiles. In this paper, we aim to compare the life cycle greenhouse gas emissions of pulp production from Finnish boreal hardwood and from South American eucalyptus. Special emphasis was placed on analysing the contribution of transport to overall climate impacts.     

Including CO<Subscript>2</Subscript>-emission equivalence of changes in land surface albedo in life cycle assessment. Methodology and case study on greenhouse agriculture

Purpose  

Climate change impacts in life cycle assessment (LCA) are usually assessed as the emissions of greenhouse gases expressed with the global warming potential (GWP). However, changes in surface albedo caused by land use change can also contribute to change the Earth’s energy budget. In this paper we present a methodology for including in LCA the climatic impacts of land surface albedo changes, measured as CO₂-eq. emissions or emission offsets.     

Measuring ecological impact of water consumption by bioethanol using life cycle impact assessment

Purpose  

Though the development of biofuel has attracted numerous studies for quantifying potential water demand applying life cycle thinking, the impacts of biofuel water consumption still remain unknown. In this study, we aimed to quantify ecological impact associated with corn-based bioethanol water consumption in Minnesota in responding to different refinery expansion scenarios by applying a life cycle impact assessment method.     

Life cycle assessment of single use thermoform boxes made from polystyrene (PS), polylactic acid, (PLA), and PLA/starch: cradle to consumer gate

Purpose

Currently, the bio-based plastics have been drawing considerable attention from the packaging industry as a sustainable solution for replacing petroleum-based plastics in order to reduce the accumulation of plastic waste in the environment. This work has benchmarked the environmental impact of bio-based against petroleum-based plastics for single use boxes. In this paper, the cradle to consumer gate environmental impact data of these boxes was calculated and reported as part 1. End-of-life options of both bio- and petroleum-based boxes are an important subject which will be further studied for part 2. The energy sources in this work were taken from the Thailand energy database namely: Thai electricity grid mix (TEGM), Thai coal electricity (TCE), Thai natural gas combine cycle (TNGCC), and Thai coal integrated gasification combine cycle (TIGCC).

Methods

The materials studied were polystyrene (PS) derived from petroleum, polylactic acid (PLA) derived from corn, and PLA/cassava starch blend (PLA/starch). The tray with lid (herein after called box) was processed in a plastic manufacturing in Thailand using cast sheet extrusion and then thermoforming techniques. The functional unit is specified as 10,000 units of 8.0?×?10.0?×?2.5 cm of PS, PLA, and PLA/starch boxes which weigh 447.60, 597.60, and 549.56 kg, respectively. Three impact categories; namely global warming potential including direct greenhouse gas, and indirect land use change (LUC) emissions, acidification, and photochemical ozone formation are investigated. Finally, the normalization results including and excluding LUC consideration were compared and reported.

Results and discussion

The results from this study have shown that the total environmental impact including LUC emission of bio-based boxes were different when the various energy sources were supplied throughout the life cycle production stage. It can be seen that the PS box has lower environmental impact than PLA and PLA/starch boxes when TEGM, TCE, TNGCC, and TIGCC were used as energy supplied. LUC of renewable feedstocks, such as corn and cassava, were considered as the biggest impact of absolute scores of PLA and PLA/starch boxes. These results are consistent with Piemonte and Gironi (2010).

Conclusions

PLA and PLA/starch boxes give a slightly higher environmental impact than the PS box by 1.59 and 1.09 times, respectively, when LUC was not accounted in the absolute scores and clean energy TIGCC was used throughout the life cycle.     

Life cycle assessment of base–load heat sources for district heating system options

Purpose  

There has been an increased interest in utilizing renewable energy sources in district heating systems. District heating systems are centralized systems that provide heat for residential and commercial buildings in a community. While various renewable and conventional energy sources can be used in such systems, many stakeholders are interested in choosing the feasible option with the least environmental impacts. This paper evaluates and compares environmental burdens of alternative energy source options for the base–load of a district heating center in Vancouver, British Columbia (BC) using the life cycle assessment method. The considered energy sources include natural gas, wood pellet, sewer heat, and ground heat.     

Home heating in temperate Australia

Background, aim, and scope  

Home heating is an important component of life in inland temperate Australia, and firewood remains a common and relatively inexpensive fuel. However, supplies of firewood are becoming scarce, and excessive smoke pollution is becoming a problem in some places, partly due to poor management of fires. The alternative energy sources are electricity and gas, and the aim of this study is to compare the relative merits of these three energy sources for their impacts on the physical environment.     

Overdispersed logistic regression for SAGE: Modelling multiple groups and covariates

Background  

Two major identifiable sources of variation in data derived from the Serial Analysis of Gene Expression (SAGE) are within-library sampling variability and between-library heterogeneity within a group. Most published methods for identifying differential expression focus on just the sampling variability. In recent work, the problem of assessing differential expression between two groups of SAGE libraries has been addressed by introducing a beta-binomial hierarchical model that explicitly deals with both of the above sources of variation. This model leads to a test statistic analogous to a weighted two-sample t-test. When the number of groups involved is more than two, however, a more general approach is needed.     

Enzymatic hydrolyzing performance of Acremonium cellulolyticus and Trichoderma reesei against three lignocellulosic materials

Background  

Bioethanol isolated from lignocellulosic biomass represents one of the most promising renewable and carbon neutral alternative liquid fuel sources. Enzymatic saccharification using cellulase has proven to be a useful method in the production of bioethanol. The filamentous fungi Acremonium cellulolyticus and Trichoderma reesei are known to be potential cellulase producers. In this study, we aimed to reveal the advantages and disadvantages of the cellulase enzymes derived from these fungi.     

Optimization algorithms for functional deimmunization of therapeutic proteins

Background  

To develop protein therapeutics from exogenous sources, it is necessary to mitigate the risks of eliciting an anti-biotherapeutic immune response. A key aspect of the response is the recognition and surface display by antigen-presenting cells of epitopes, short peptide fragments derived from the foreign protein. Thus, developing minimal-epitope variants represents a powerful approach to deimmunizing protein therapeutics. Critically, mutations selected to reduce immunogenicity must not interfere with the protein's therapeutic activity.