in Wiley Online Library (wileyonlinelibrary.com).This article addresses the optimal design and planning of cellulosic ethanol supply chains under economic, environmental, and social objectives. The economic objective is measured by the total annualized cost, the environmental objective is measured by the life cycle greenhouse gas emissions, and the social objective is measured by the number of accrued local jobs. A multiobjective mixed-integer linear programming (mo-MILP) model is developed that accounts for major characteristics of cellulosic ethanol supply chains, including supply seasonality and geographical diversity, biomass degradation, feedstock density, diverse conversion pathways and byproducts, infrastructure compatibility, demand distribution, regional economy, and government incentives. Aspen Plus models for biorefineries with different feedstocks and conversion pathways are built to provide detailed techno-economic and emission analysis results for the mo-MILP model, which simultaneously predicts the optimal network design, facility location, technology selection, capital investment, production planning, inventory control, and logistics management decisions. The mo-MILP problem is solved with an econstraint method; and the resulting Pareto-optimal curves reveal the tradeoff between the economic, environmental, and social dimensions of the sustainable biofuel supply chains. The proposed approach is illustrated through two case studies for the state of Illinois.We note that both distance variable costs and distance fixed costs are taken into account in the feedstock and fuel ethanol

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a b s t r a c tRecently the United States Environmental Protection Agency qualified biogas from landfills and anaerobic digesters as a cellulosic transportation biofuel under the expanded Renewable Fuel Standard (RFS2). Biogas is a renewable fuel that can generate Renewable Identification Number credits for the producer. The wastewater industry may not be able to keep pace with this opportunity. Less than 10% of WWTPs in the US have currently produced biogas for beneficial use. Supporting growth of the biogas industry requires implementation of new practices and policies. In this review, the barriers, gaps, and challenges in deploying biogas production technology are identified. Issues are classified as economic, technical, social or regulatory issues. Some of the critical challenges to the economics of digester operations are the slow rate of biogas generation, the low energy content of the biogas, and the costs to upgrade the biogas.Currently there is little biogas utilization at US WWTPs. Most biogas is flared while some is used for onsite process heat and power production. Case studies of co-digestion of biosolids with organic wastes at field-scale show the use of co-digestion could overcome significant economic challenges including higher methane yield, more efficient digester volume utilization and reduced biosolids production. These findings could provide guidance in retrofitting existing facilities or in designing new biogas production and utilization systems. The RFS2 ruling increases market certainty, hence reduces risk. The evaluation of applications of co-digestion at WWTP scales ranging from 1 million gallons per day (MGD) to 375 MGD determined its potential feasibility for different types of digester operation, organic waste and loading rate as well as effectiveness of providing energy self-sufficiency at the WWTPs. This work could improve economics of anaerobic digestion at WWTPs, enabling viable and sustainable biogas industry and offsetting costs for wastewater management.

To achieve food and energy security, sustainable bioenergy has become an important goal for many countries. The use of marginal lands to produce energy crops is one strategy for achieving this goal, but what is marginal land? Current definitions generally focus on a single criterion, primarily agroeconomic profitability. Herein, we present a framework that incorporates multiple criteria including profitability of current land use, soil health indicators (erosion, flooding, drainage, or high slopes), and environmental degradation resulting from contamination of surface water or groundwater resources. We tested this framework for classifying marginal land in the state of Nebraska and estimated the potential for using marginal land to produce biofuel crops. Our results indicate that approximately 1.6 million ha, or 4 million acres, of land (approximately 8% of total land area) could be classified as marginal on the basis of at least two criteria. Second-generation lignocellulosic bioenergy crops such as switchgrass ( Panicum virgatum L.), miscanthus (Miscanthus giganteus), native prairie grasses, and short-rotation woody crops could be grown on this land in redesigned landscapes that meet energy and environmental needs, without significant impacts on food or feed production. Calculating tradeoffs between the economics of redesigned landscapes and current practices at the field scale is the next step for determining functional designs for integrating biofuel feedstock production into current land management practices.

h i g h l i g h t sA novel anaerobic digestion (AD) process with in-situ biogas cleanup and upgrading is developed. Biochar-amended digester produced pipeline-quality (>90% CH 4 , <5 ppb H 2 S) biomethane. Corn stover biochar addition sequesters CO 2 and enhances CH 4 yield for sludge AD. Biochar addition increases alkalinity and mitigates NH 3 inhibition in the digester. Digestate from biochar-amended digester is nutrient-enriched and can be used for soil application. a b s t r a c tThis study presents a novel process for producing pipeline-quality biomethane by anaerobic digestion (AD) of sludge with in-situ biogas cleanup and upgrading using corn stover biochar. The biochar has high surface area (105 m 2 /g), high ash content (45.2% dry weight) and high concentrations of potassium, calcium and magnesium (14.2% K 2 O, 3.9% CaO and 4.2% MgO of the ash content, respectively). The biocharamended digesters produced near pipeline-quality biomethane (>90% CH 4 and <5 ppb H 2 S), facilitated CO 2 removal by up to 86.3%, boosted average CH 4 content in biogas by up to 42.4% compared to the control digester, close to fungibility of natural gas. The biochar addition enhanced the methane yield, biomethanation rate constant and maximum methane production rate by up to 7.0%, 8.1% and 27.6%, respectively. The biochar addition also increased alkalinity and mitigated ammonia inhibition, providing sustainable process stability for thermophilic sludge AD. The biochar-amended digestate is enriched with nutrients such as potassium, nitrogen and phosphorus, and therefore has great potential for soil applications.