Long-term bioethanol system and its implications on GHG emissions: a case study of Thailand

The study evaluates greenhouse gas (GHG) emissions performance of future bioethanol systems in Thailand to ascertain whether bioethanol for transport could help the country mitigate a global warming impact. GHG emission factors of bioethanol derived from cassava, molasses, and sugar cane are analyzed using 12 scenarios covering the critical variables possibly affecting the GHG performance, i.e., (1) the possible direct land use change caused by expanding feedstock cultivation areas; (2) types of energy carriers used in ethanol plants; and (3) waste utilization, e.g., biogas recovery and dry distillers grains with solubles (DDGS) production. The assessment reveals that GHG performance of a Thai bioethanol system is inclined to decrease in the long run due to the effects from the expansion of plantation areas to satisfy the deficit of cassava and molasses. Therefore, bioethanol will contribute to the country's strategic plan on GHG mitigation in the transportation sector only if the production systems are sustainably managed, i.e., coal replaced by biomass in ethanol plants, biogas recovery, and adoption of improved agricultural practices to increase crop productivity without intensification of chemical fertilizers. Achieving the year 2022 government policy targets for bioethanol with recommended measures would help mitigate GHG emissions up to 4.6 Gg CO(2)-eq per year.     

Impact of aviation non-CO₂ combustion effects on the environmental feasibility of alternative jet fuels

Alternative fuels represent a potential option for reducing the climate impacts of the aviation sector. The climate impacts of alternatives fuel are traditionally considered as a ratio of life cycle greenhouse gas (GHG) emissions to those of the displaced petroleum product; however, this ignores the climate impacts of the non-CO(2) combustion effects from aircraft in the upper atmosphere. The results of this study show that including non-CO(2) combustion emissions and effects in the life cycle of a Synthetic Paraffinic Kerosene (SPK) fuel can lead to a decrease in the relative merit of the SPK fuel relative to conventional jet fuel. For example, an SPK fuel option with zero life cycle GHG emissions would offer a 100% reduction in GHG emissions but only a 48% reduction in actual climate impact using a 100-year time window and the nominal climate modeling assumption set outlined herein. Therefore, climate change mitigation policies for aviation that rely exclusively on relative well-to-wake life cycle GHG emissions as a proxy for aviation climate impact may overestimate the benefit of alternative fuel use on the global climate system.     

Land use greenhouse gas emissions from conventional oil production and oil sands

Debates surrounding the greenhouse gas (GHG) emissions from land use of biofuels production have created a need to quantify the relative land use GHG intensity of fossil fuels. When contrasting land use GHG intensity of fossil fuel and biofuel production, it is the energy yield that greatly distinguishes the two. Although emissions released from land disturbed by fossil fuels can be comparable or higher than biofuels, the energy yield of oil production is typically 2-3 orders of magnitude higher, (0.33-2.6, 0.61-1.2, and 2.2 5.1 PJ/ha) for conventional oil production, oil sands surface mining, and in situ production, respectively). We found that land use contributes small portions of GHGs to life cycle emissions of California crude and in situ oil sands production ( <0.4% or < 0.4 gCO?e/MJ crude refinery feedstock) and small to modest portions for Alberta conventional oil (0.1-4% or 0.1-3.4 gCO?e/MJ) and surface mining of oil sands (0.9-11% or 0.8-10.2 gCO?e/MJ).Our estimates are based on assumptions aggregated over large spatial and temporal scales and assuming 100% reclamation. Values on finer spatial and temporal scales that are relevant to policy targets need to account for site-specific information, the baseline natural and anthropogenic disturbance.     

Densified biomass can cost-effectively mitigate greenhouse gas emissions and address energy security in thermal applications

Regional supplies of biomass are currently being evaluated as feedstocks in energy applications to meet renewable portfolio (RPS) and low carbon fuel standards. We investigate the life cycle greenhouse gas (GHG) emissions and associated abatement costs resulting from using densified switchgrass for thermal and electrical energy. In contrast to the large and positive abatement costs for using biomass in electricity generation ($149/Mg CO(2)e) due to the low cost of coal and high feedstock and power plant operation costs, abatement costs for replacing fuel oil with biomass in thermal applications are large and negative (-$52 to -$92/Mg CO(2)e), resulting in cost savings. Replacing fuel oil with biomass in thermal applications results in least cost reductions compared to replacing coal in electricity generation, an alternative that has gained attention due to RPS legislation and the centralized production model most often considered in U.S. policy. Our estimates indicate a more than doubling of liquid fuel displacement when switchgrass is substituted for fuel oil as opposed to gasoline, suggesting that, in certain U.S. locations, such as the northeast, densified biomass would help to significantly decarbonize energy supply with regionally sourced feedstock, while also reducing imported oil. On the basis of supply projections from the recently released Billion Ton Report, there will be enough sustainably harvested biomass available in the northeast by 2022 to offset the entirety of heating oil demand in the same region. This will save NE consumers between $2.3 and $3.9 billion annually. Diverting the same resource to electricity generation would cost the region $7.7 billion per year. While there is great need for finding low carbon substitutes for coal power and liquid transportation fuels in the U.S., we argue that in certain regions it makes cost- (and GHG mitigation-) effective sense to phase out liquid heating fuels with locally produced biomass first.     

Methods to determine the relative value of genetic traits in dairy cows to reduce greenhouse gas emissions along the chain

Current decisions on breeding in dairy farming are mainly based on economic values of heritable traits, as earning an income is a primary objective of farmers. Recent literature, however, shows that breeding also has potential to reduce greenhouse gas (GHG) emissions. The objective of this paper was to compare 2 methods to determine GHG values of genetic traits. Method 1 calculates GHG values using the current strategy (i.e., maximizing labor income), whereas method 2 is based on minimizing GHG per kilogram of milk and shows what can be achieved if the breeding results are fully directed at minimizing GHG emissions. A whole-farm optimization model was used to determine results before and after 1 genetic standard deviation improvement (i.e., unit change) of milk yield and longevity. The objective function of the model differed between method 1 and 2. Method 1 maximizes labor income; method 2 minimizes GHG emissions per kilogram of milk while maintaining labor income and total milk production at least at the level before the change in trait. Results show that the full potential of the traits to reduce GHG emissions given the boundaries that were set for income and milk production (453 and 441 kg of CO₂ equivalents/unit change per cow per year for milk yield and longevity, respectively) is about twice as high as the reduction based on maximizing labor income (247 and 210 kg of CO₂ equivalents/unit change per cow per year for milk yield and longevity, respectively). The GHG value of milk yield is higher than that of longevity, especially when the focus is on maximizing labor income. Based on a sensitivity analysis, it was shown that including emissions from land use change and using different methods for handling the interaction between milk and meat production can change results, generally in favor of milk yield. Results can be used by breeding organizations that want to include GHG values in their breeding goal. To verify GHG values, the effect of prices and emissions factors should be considered, as well as the potential effect of variation between farm types.     

Policy implications of uncertainty in modeled life-cycle greenhouse gas emissions of biofuels

Biofuels have received legislative support recently in California's Low-Carbon Fuel Standard and the Federal Energy Independence and Security Act. Both present new fuel types, but neither provides methodological guidelines for dealing with the inherent uncertainty in evaluating their potential life-cycle greenhouse gas emissions. Emissions reductions are based on point estimates only. This work demonstrates the use of Monte Carlo simulation to estimate life-cycle emissions distributions from ethanol and butanol from corn or switchgrass. Life-cycle emissions distributions for each feedstock and fuel pairing modeled span an order of magnitude or more. Using a streamlined life-cycle assessment, corn ethanol emissions range from 50 to 250 g CO(2)e/MJ, for example, and each feedstock-fuel pathway studied shows some probability of greater emissions than a distribution for gasoline. Potential GHG emissions reductions from displacing fossil fuels with biofuels are difficult to forecast given this high degree of uncertainty in life-cycle emissions. This uncertainty is driven by the importance and uncertainty of indirect land use change emissions. Incorporating uncertainty in the decision making process can illuminate the risks of policy failure (e.g., increased emissions), and a calculated risk of failure due to uncertainty can be used to inform more appropriate reduction targets in future biofuel policies.     

Reducing greenhouse gas emissions through genetic selection in the Australian dairy industry

This research explores possible options to reduce greenhouse gas (GHG) emissions in the Australian dairy industry by (1) including an environmental component in the national breeding program and (2) estimating the economic and environmental impacts of implementation of the subsequent indexes. A total of 12 possible selection indexes were considered. These indexes were developed to predict changes in gross per-animal methane production (using 3 scenarios depending on availability and efficacy of a direct methane trait breeding value prediction) with 4 different carbon prices, integrating them into an augmentation of the current conventional national selection index. Although some economic response is lost with inclusion of the GHG subindexes in the Balanced Performance Index, options do exist where this loss is marginal and, even in scenarios where all selection pressure is based on the environmental weighting, economic progress is still made in all cases. When including environmental traits within an index, if a relatively low percentage of economic gain or index progression is sacrificed, then approximately 40 to 50% of the maximum possible reductions in emissions may be achieved. This concurrent selection of estimated breeding values that have a correlated favorable response in emissions in addition to direct selection on a residual methane trait allows a high level of methane reduction to be achieved with a realized cost to farmers that is far lower than the economic value placed on carbon. By implementing a GHG subindex in the national breeding program, we can achieve up to a 7.9% decrease in residual methane and 9 times the reduction in gross emissions in 10 yr, compared with the current breeding program, with little to no cost to farmers. By 2050, selection based on one of the more moderate index scenarios at a carbon price of AUD$250/t (AUD$1 = US$0.71), or opportunity cost to farmers of AUD$87.22, will reduce gross emissions by 8.23% and emissions intensity by 21.25%, therefore offering a mitigation strategy that will be effective at reducing emissions with little compromise to profit.     

Variability and uncertainty in life cycle assessment models for greenhouse gas emissions from Canadian oil sands production

Because of interest in greenhouse gas (GHG) emissions from transportation fuels production, a number of recent life cycle assessment (LCA) studies have calculated GHG emissions from oil sands extraction, upgrading, and refining pathways. The results from these studies vary considerably. This paper reviews factors affecting energy consumption and GHG emissions from oil sands extraction. It then uses publicly available data to analyze the assumptions made in the LCA models to better understand the causes of variability in emissions estimates. It is found that the variation in oil sands GHG estimates is due to a variety of causes. In approximate order of importance, these are scope of modeling and choice of projects analyzed (e.g., specific projects vs industry averages); differences in assumed energy intensities of extraction and upgrading; differences in the fuel mix assumptions; treatment of secondary noncombustion emissions sources, such as venting, flaring, and fugitive emissions; and treatment of ecological emissions sources, such as land-use change-associated emissions. The GHGenius model is recommended as the LCA model that is most congruent with reported industry average data. GHGenius also has the most comprehensive system boundaries. Last, remaining uncertainties and future research needs are discussed.     

Beef production in balance: considerations for life cycle analyses

Life Cycle Assessments (LCA) are useful tools to analyze a product's "carbon footprint" (e.g., the net greenhouse gas (GHG) emissions expressed as standardized carbon dioxide equivalents per unit of product) considering all phases of the production chain. For beef, an LCA would include the GHG emissions from feed production, from the enteric fermentation of the cattle, from the cattle's waste, and from processing and transportation. Identifying the scope and scale of the LCA is critical and key to preventing inappropriate applications of the analysis (e.g., applying a global LCA for beef to the regional or national scale). Ideally, a LCA can integrate the complex biogeochemical processes responsible for GHG emissions and the disparate animal and agricultural management techniques used be different phases of the beef production chain (e.g., feedlot vs. cow-calf) and different production systems (e.g., conventional vs. organic).     

Parametric assessment of climate change impacts of automotive material substitution

Quantifying the net climate change impact of automotive material substitution is not a trivial task. It requires the assessment of the mass reduction potential of automotive materials, the greenhouse gas (GHG) emissions from their production and recycling, and their impact on GHG emissions from vehicle use. The model presented in this paper is based on life cycle assessment (LCA) and completely parameterized, i.e., its computational structure is separated from the required input data, which is not traditionally done in LCAs. The parameterization increases scientific rigor and transparency of the assessment methodology, facilitates sensitivity and uncertainty analysis of the results, and also makes it possible to compare different studies and explain their disparities. The state of the art of the modeling methodology is reviewed and advanced. Assessment of the GHG emission impacts of material recycling through consequential system expansion shows that our understanding of this issue is still incomplete. This is a critical knowledge gap since a case study shows thatfor materials such as aluminum, the GHG emission impacts of material production and recycling are both of the same size as the use phase savings from vehicle mass reduction.     

Regional analysis of greenhouse gas emissions from USA dairy farms: A cradle to farm-gate assessment of the American dairy industry circa 2008

Greenhouse gas (GHG) emissions were evaluated from crop production through the on-farm portion of the milk supply chain for five production regions in the USA derived from publicly available data and from 536 surveys of farm operations collected from dairy operations nationwide. The production weighted national average footprint at the farm gate was 1.23 kg carbon dioxide equivalent (CO₂e) per kg of fat and protein corrected milk (fat, 4%; protein 3.3%). Regional differences in GHG emissions per kg milk produced can be primarily traced to differences in production and management practices. Feed-to-milk conversion efficiency is shown to be the single most important explanatory variable, followed by choice of manure management technology. While there is no one-size-fits-all solution, GHG emissions reduction opportunities exist across the spectrum of dairy management options. However, as with all decisions, it is important to weigh potential trade-offs with other environmental and economic impacts.     

Calculator tool for determining greenhouse gas emissions for biosolids processing and end use

A greenhouse gas (GHG) calculator tool (Biosolids Emissions Assessment Model, BEAM) was developed for the Canadian Council of Ministers of the Environment to allow municipalities to estimate GHG emissions from biosolids management. The tool was developed using data from peer reviewed literature and municipalities. GHG emissions from biosolids processing through final end use/disposal were modeled. Emissions from nine existing programs in Canada were estimated using the model. The program that involved dewatering followed by combustion resulted in the highest GHG emissions (Mg CO(2)e 100 Mg(-1) biosolids (dry wt.). The programs that had digestion followed by land application resulted in the lowest emissions (-26 and -23 Mg CO(2)e 100 Mg(-1) biosolids (dry wt.). Transportation had relatively minor effects on overall emissions. The greatest areas of uncertainty in the model include N(2)O emissions from land application and biosolids processing. The model suggests that targeted use of biosolids and optimizing processes to avoid CH(4) and N(2)O emissions can result in significant GHG savings.     

Food-miles and the relative climate impacts of food choices in the United States

Despite significant recent public concern and media attention to the environmental impacts of food, few studies in the United States have systematically compared the life-cycle greenhouse gas (GHG) emissions associated with food production against long-distance distribution, aka "food-miles." We find that although food is transported long distances in general (1640 km delivery and 6760 km life-cycle supply chain on average) the GHG emissions associated with food are dominated by the production phase, contributing 83% of the average U.S. household's 8.1 t CO2e/yr footprint for food consumption. Transportation as a whole represents only 11% of life-cycle GHG emissions, and final delivery from producer to retail contributes only 4%. Different food groups exhibit a large range in GHG-intensity; on average, red meat is around 150% more GHG-intensive than chicken or fish. Thus, we suggest that dietary shift can be a more effective means of lowering an average household's food-related climate footprint than "buying local." Shifting less than one day per week's worth of calories from red meat and dairy products to chicken, fish, eggs, or a vegetable-based diet achieves more GHG reduction than buying all locally sourced food.     

Greenhouse gas emissions from milk production and consumption in the United States: A cradle-to-grave life cycle assessment circa 2008

This article presents a cradle-to-grave analysis of the United States fluid milk supply chain greenhouse gas (GHG) emissions that are accounted from fertilizer production through consumption and disposal of milk packaging. Crop production and on-farm GHG emissions were evaluated using public data and 536 farm operation surveys. Milk processing data were collected from 50 dairy plants nationwide. Retail and consumer GHG emissions were estimated from primary data, design estimates, and publicly available data. Total GHG emissions, based primarily on 2007 to 2008 data, were 2.05 (90% confidence limits: 1.77–2.4) kg CO₂e per kg milk consumed, which accounted for loss of 12% at retail and an additional 20% loss at consumption. A complementary analysis showed the entire dairy sector contributes approximately 1.9% of US GHG emissions. While the largest GHG contributors are feed production, enteric methane, and manure management; there are opportunities to reduce impacts throughout the supply chain.     

Co-control of urban air pollutants and greenhouse gases in Mexico City

This study addresses the synergies of mitigation measures to control urban air pollutant and greenhouse gas (GHG) emissions, in developing integrated "co-control" strategies for Mexico City. First, existing studies of emissions reduction measures--PROAIRE (the air quality plan for Mexico City) and separate GHG studies--are used to construct a harmonized database of options. Second, linear programming (LP) is developed and applied as a decision-support tool to analyze least-cost strategies for meeting co-control targets for multiple pollutants. We estimate that implementing PROAIRE measures as planned will reduce 3.1% of the 2010 metropolitan CO2 emissions, in addition to substantial local air pollutant reductions. Applying the LP, PROAIRE emissions reductions can be met at a 20% lower cost, using only the PROAIRE measures, by adjusting investments toward the more cost-effective measures; lower net costs are possible by including cost-saving GHG mitigation measures, but with increased investment. When CO2 emission reduction targets are added to PROAIRE targets, the most cost-effective solutions use PROAIRE measures for the majority of local pollutant reductions, and GHG measures for additional CO2 control. Because of synergies, the integrated planning of urban-global co-control can be beneficial, but we estimate that for Mexico City these benefits are often small.     

Sustainability and energy development: influences of greenhouse gas emission reduction options on water use in energy production

Climate change mitigation strategies cannot be evaluated solely in terms of energy cost and greenhouse gas (GHG) mitigation potential. Maintaining GHGs at a "safe" level will require fundamental change in the way we approach energy production, and a number of environmental, economic, and societal factors will come into play. Water is an essential component of energy production, and water resource constraints will limit our options for meeting society's growing demand for energy while also reducing GHG emissions. This study evaluates these potential constraints from a global perspective by revisiting the climate wedges proposal of Pacala and Socolow (Science2004, 305 (5686), 968-972) and evaluating the potential water-use impacts of the wedges associated with energy production. GHG mitigation options that improve energy conversion or use efficiency can simultaneously reduce GHG emissions, lower energy costs, and reduce energy impacts on water resources. Other GHG mitigation options (e.g., carbon capture and sequestration, traditional nuclear, and biofuels from dedicated energy crops) increase water requirements for energy. Achieving energy sustainability requires deployment of alternatives that can reduce GHG emissions, water resource impacts, and energy costs.     

Converting oil shale to liquid fuels: energy inputs and greenhouse gas emissions of the Shell in situ conversion process

Oil shale is a sedimentary rock that contains kerogen, a fossil organic material. Kerogen can be heated to produce oil and gas (retorted). This has traditionally been a CO2-intensive process. In this paper, the Shell in situ conversion process (ICP), which is a novel method of retorting oil shale in place, is analyzed. The ICP utilizes electricity to heat the underground shale over a period of 2 years. Hydrocarbons are produced using conventional oil production techniques, leaving shale oil coke within the formation. The energy inputs and outputs from the ICP, as applied to oil shales of the Green River formation, are modeled. Using these energy inputs, the greenhouse gas (GHG) emissions from the ICP are calculated and are compared to emissions from conventional petroleum. Energy outputs (as refined liquid fuel) are 1.2-1.6 times greater than the total primary energy inputs to the process. In the absence of capturing CO2 generated from electricity produced to fuel the process, well-to-pump GHG emissions are in the range of 30.6-37.1 grams of carbon equivalent per megajoule of liquid fuel produced. These full-fuel-cycle emissions are 21%-47% larger than those from conventionally produced petroleum-based fuels.     

Greenhouse gas emissions and land use change from Jatropha curcas-based jet fuel in Brazil

This analysis presents a comparison of life-cycle GHG emissions from synthetic paraffinic kerosene (SPK) produced as jet fuel substitute from jatropha curcas feedstock cultivated in Brazil against a reference scenario of conventional jet fuel. Life cycle inventory data are derived from surveys of actual Jatropha growers and processors. Results indicate that a baseline scenario, which assumes a medium yield of 4 tons of dry fruit per hectare under drip irrigation with existing logistical conditions using energy-based coproduct allocation methodology, and assumes a 20-year plantation lifetime with no direct land use change (dLUC), results in the emissions of 40 kg CO?e per GJ of fuel produced, a 55% reduction relative to conventional jet fuel. However, dLUC based on observations of land-use transitions leads to widely varying changes in carbon stocks ranging from losses in excess of 50 tons of carbon per hectare when Jatropha is planted in native cerrado woodlands to gains of 10-15 tons of carbon per hectare when Jatropha is planted in former agro-pastoral land. Thus, aggregate emissions vary from a low of 13 kg CO?e per GJ when Jatropha is planted in former agro-pastoral lands, an 85% decrease from the reference scenario, to 141 kg CO?e per GJ when Jatropha is planted in cerrado woodlands, a 60% increase over the reference scenario. Additional sensitivities are also explored, including changes in yield, exclusion of irrigation, shortened supply chains, and alternative allocation methodologies.     

Environmental impacts of cultured meat production

Cultured meat (i.e., meat produced in vitro using tissue engineering techniques) is being developed as a potentially healthier and more efficient alternative to conventional meat. Life cycle assessment (LCA) research method was used for assessing environmental impacts of large-scale cultured meat production. Cyanobacteria hydrolysate was assumed to be used as the nutrient and energy source for muscle cell growth. The results showed that production of 1000 kg cultured meat requires 26-33 GJ energy, 367-521 m(3) water, 190-230 m(2) land, and emits 1900-2240 kg CO(2)-eq GHG emissions. In comparison to conventionally produced European meat, cultured meat involves approximately 7-45% lower energy use (only poultry has lower energy use), 78-96% lower GHG emissions, 99% lower land use, and 82-96% lower water use depending on the product compared. Despite high uncertainty, it is concluded that the overall environmental impacts of cultured meat production are substantially lower than those of conventionally produced meat.     

Scenario projections for future market potentials of biobased bulk chemicals

Three scenario projections for future market potentials of biobased bulk chemicals produced by means of white biotechnology are developed for Europe (EU-25) until the year 2050, and potential nonrenewable energy savings, greenhouse gas emission reduction, and land use consequences are analyzed. These scenarios assume benign, moderate, and disadvantageous conditions for biobased chemicals. The scenario analysis yields a broad range of values for the possible market development of white biotechnology chemicals, that is, resulting in a share of white biotechnology chemicals relative to all organic chemicals of about 7 (or 5 million tonnes), 17.5 (or 26 million tonnes), or 38% (or 113 million tonnes) in 2050. We conclude that under favorable conditions, white biotechnology enables substantial savings of nonrenewable energy use (NREU) and greenhouse gas (GHG) emissions compared to the energy use of the future production of all organic chemicals from fossil resources. Savings of NREU reach up to 17% for starch crops and up to 31% for lignocellulosic feedstock by 2050, and saving percentages for GHG emissions are in a similar range. Parallel to these environmental benefits, economic advantages of up to 75 billion Euro production cost savings arise.