15 Search Results

Abstract Corn kernel fiber ethanol that can be produced concurrently with corn starch ethanol has recently been approved as cellulosic biofuel in the USA, suggesting that fiber ethanol could be eligible for a higher credit price than conventional starch ethanol due to its anticipated lower greenhouse gas (GHG) emissions. A life‐cycle analysis was conducted to quantify ethanol's GHG emissions. Here we show that fiber ethanol's life‐cycle GHG emissions (36–39 g CO ₂ e MJ ⁻¹ ) are close to meeting the US cellulosic biofuel's legislative mandate of 60% GHG emissions reduction relative to gasoline (~94 g CO ₂ e MJmore » ⁻¹ ), with slightly lower emissions under the nth plant mature fiber technology than under the state of technology (SOT). The co‐product, distiller's grain with solubles (DGS), can notably affect fiber ethanol's GHG emissions, and this impact may need to be further examined when evidence of DGS market impacts becomes available. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd« less

Abstract New integrated biorefinery (IBR) concepts are being investigated to co‐produce hydrocarbon fuels and high‐value bio‐based chemicals to improve the economic viability of IBRs, to enhance biomass resource utilization efficiencies, and to maximize potential greenhouse gas (GHG) emission reductions. Unlike fuel‐only biorefineries, IBRs may co‐produce a significant amount of bio‐based chemicals, whose emission implications for specific biorefinery products and the biorefinery as a whole need to be evaluated. We discuss this in principle and apply three sets of co‐product handling methods to conduct life‐cycle analysis (LCA) of modeled IBRs with co‐production of two bioproduct examples – succinic acid and adipicmore » acid – alongside a renewable diesel blendstock fuel product. The LCA results for the specific co‐product handling methods that were examined shed light on potential artifacts of product‐specific LCA with selected co‐product methods. We discuss the advantages and limitations of each method and conclude that (i) a system‐level or ‘black‐box’ LCA allocation method is too simplistic to reflect appropriately the GHG burdens of distinctly different processing trains for fuels and chemicals in the IBR context, and (ii) the displacement method is the only co‐product handling method that accounts fully for the emission effects of both the fuel product and the non‐fuel bio‐based co‐products in the IBRs within the context of the existing fuel‐focused GHG regulatory framework. Alternatively, biorefinery system‐level LCA combines benefits of individual products to offer a complete picture. This system‐level LCA approach offers a holistic LCA without somewhat arbitrary decisions either on an allocation basis or by the selection of an evaluation metric based on specific products. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.« less

Water is an essential resource for most electric power generation technologies. Thermal power plants typically require a large amount of cooling water whose evaporation is regarded to be consumed. Hydropower plants result in evaporative water loss from the large surface areas of the storing reservoirs. This paper estimated the regional water consumption factors (WCFs) for thermal and hydro electricity generation in the United States, because the WCFs of these power plants vary by region and water supply and demand balance are of concern in many regions. For hydropower, total WCFs were calculated using a reservoir’s surface area, state-level water evaporation,more » and background evapotranspiration. Then, for a multipurpose reservoir, a fraction of its WCF was allocated to hydropower generation based on the share of the economic valuation of hydroelectricity among benefits from all purposes of the reservoir. For thermal power plants, the variations in WCFs by type of cooling technology, prime mover technology, and by region were addressed. The results show that WCFs for electricity generation vary significantly by region. Finally, the generation-weighted average WCFs of thermoelectricity and hydropower are 1.25 (range of 0.18–2.0) and 16.8 (range of 0.67–1194) L/kWh, respectively, and the generation-weighted average WCF by the U.S. generation mix in 2015 is estimated at 2.18 L/kWh.« less

Abstract Harvesting corn stover for biofuel production may decrease soil organic carbon ( SOC ) and increase greenhouse gas ( GHG ) emissions. Adding additional organic matter into soil or reducing tillage intensity, however, could potentially offset this SOC loss. Here, using SOC and life cycle analysis ( LCA ) models, we evaluated the impacts of land management change ( LMC ), that is, stover removal, organic matter addition, and tillage on spatially explicit SOC level and biofuels’ overall life cycle GHG emissions in US corn–soybean production systems. Results indicate that under conventional tillage ( CT ), 30% stover removalmore » (dry weight) may reduce baseline SOC by 0.04 t C ha ⁻¹  yr ⁻¹ over a 30‐year simulation period. Growing a cover crop during the fallow season or applying manure, on the other hand, could add to SOC and further reduce biofuels’ life cycle GHG emissions. With 30% stover removal in a CT system, cover crop and manure application can increase SOC at the national level by about 0.06 and 0.02 t C ha ⁻¹  yr ⁻¹ , respectively, compared to baseline cases without such measures. With contributions from this SOC increase, the life cycle GHG emissions for stover ethanol are more than 80% lower than those of gasoline, exceeding the US Renewable Fuel Standard mandate of 60% emissions reduction in cellulosic biofuels. Reducing tillage intensity while removing stover could also limit SOC loss or lead to SOC gain, which would lower stover ethanol life cycle GHG emissions to near or under the mandated 60% reduction. Without these organic matter inputs or reduced tillage intensity, however, the emissions will not meet this mandate. More efforts are still required to further identify key practical LMC s, improve SOC modeling, and accounting for LMC s in biofuel LCA s that incorporate stover removal.« less

Plastic-to-fuel (PTF) technology uses pyrolysis to convert plastic waste—especially non-recycled plastics (NRP)—into ultra-low sulfur diesel (ULSD) fuel. To assess the potential energy and environmental benefits associated with PTF technology, we calculated the energy, water consumption, and greenhouse gas emissions of NRP-derived ULSD and compared the results to those metrics for conventional ULSD fuel. For these analyses, we used the Greenhouse gases, Regulated Emissions and Energy use in Transportation (GREET®) model. Five companies provided pyrolysis process product yields and material and energy consumption data. Co-products of the process included char and fuel gas. Char can be landfilled, which, per the companymore » responses, is the most common practice for this co-product, or it may be sold as an energy product. Fuel gas can be combusted to internally generate process heat and electricity. Sensitivity analyses investigated the influence of co-product handling methodology, product yield, electric grid composition, and assumed efficiency of char combustion technology on life-cycle greenhouse gas emissions. The sensitivity analysis indicates that the GHG emissions would likely be reduced up to 14% when it is compared to conventional ULSD, depending on the co-product treatment method used. NRP-derived ULSD fuel could therefore be considered at a minimum carbon neutral with the potential to offer a modest GHG reduction. Moreover, this waste-derived fuel had 58% lower water consumption and up to 96% lower fossil fuel consumption than conventional ULSD fuel in the base case. In addition to the comparison of PTF fuels with conventional transportation fuels, we also compare the results with alternative scenarios for managing NRP including power generation and landfilling in the United States.« less