Balancing the Use of Crop Residues for Biofuels with Impacts on Soil and Greenhouse Gases

by Jessica Bass

The use of crop residues as a second-generation source of biofuels may hold potential to help the United States fulfill its 2022 goal production quota outlined in the 2007 Energy Independence and Security Act. Yet, this annual accumulation plays an important role toward maintaining soil organic carbon (SOC) stocks and reducing soil erosion, protecting field health to sustain year-after-year of yields. Adler et al. (2015) use the DayCent biogeochemical model to analyze the costs and benefits of crop residue removal and use based upon its impact on crop yield, SOC content, and N2O emissions, over the course of twenty years. They examined these relationships with respect to a variety of anticipated treatment options, including: a baseline condition with no residue removal, a sample of 50% residue removal without any replacements, 50% residue removal with a nitrogen replacement equivalent to the amount removed, and a 50% residue removal and equivalent application of a high-lignin fermentation byproduct (HLFB). Continue reading

Seasonal Energy Storage using Bioenergy Production from Abandoned Croplands

by Christina Whalen

Producing electricity from biomass could potentially provide a back-up storage source for the intermittency that accompanies wind and solar energy production. Biomass electricity also provides a carbon-negative and efficient method for bioenergy production, which is important because of mandated restrictions on carbon emissions. Furthermore, biomass electricity also provides an efficient method for providing renewable transportation energy that could replace current liquid fuel approaches. Although bioenergy may be important in producing electricity and developing energy storage mechanisms, the economic and environmental effects are unclear. Studies have been conducted on abandoned agricultural lands to try to find a path of producing bioenergy that has reduced land impact. Campbell et al. estimate at county level, the magnitude and distribution of abandoned agricultural lands in the United States and attempt to quantify how much potential energy storage could be produced by the provided bioenergy. Continue reading

Topographic and Soil Influences on Root Productivity of Three Bioenergy Cropping Systems

by Christina Whalen

Root production in plants plays a vital role in ecosystem carbon, nutrient, and water cycling, but researchers have not made much progress in further understanding this issue. It’s important to understand the impacts of environmental conditions on root production because it aids in the development of a sustainable bioeconomy. However, scaling root productivity estimates for cropping systems beyond plot scales poses a great challenge to researchers. Whether the bioenergy plants are annual or perennial influences the biogeochemical cycling and the ecological benefit of the systems. The foundation of the study is based on previous research of the response of root growth to variations in soil properties at multiple spatial scales. Roots of plants generally respond to different soil types by growing into nutrient patches, but this depends on the species and nutrient demands or limitations. Ontl et al. measured the response of root productivity of three different bioenergy cropping systems across a topographic gradient with variation in typical agroecosystem soil conditions. The hypothesis is that root dynamics would vary by cropping system and position of the landscape across a hillslope. If landscape alone was not a good enough indicator, they predicted that root productivity would be related to differences in soil. Continue reading

Hemp: A More Sustainable Annual Energy Crop for Climate and Energy Policy

by Christina Whalen

Growing concern about greenhouse gas (GHG) emissions and climate change due to fossil fuel dependency has led to the consideration of more attractive energy sources, especially bioenergy sources. In Northern Europe, the two crops that have worked the most effectively are Miscanthus and willow, two perennial energy grasses that have proven to be sustainable energy crops due to high yields of biomass from low inputs. Farmers are fairly attracted to cultivating these crops because of the declining farming market and the future promise of a biomass energy market. Farmers use break crops to control for disease and weeds, a technique that also increases wheat production. Currently sugar beet and oilseed rape are used in Northern Europe, but because of reduction in the sugar beet industry, hemp has been predicted to be an effective break crop because its root system aids soil structure. Various studies have demonstrated that it produces high yields of biomass with no agrochemical input and very little fertilizer use. It offers the potential of being an effective break crop as well as an energy crop. Finnan et al. compare hemp with other annual and perennial energy crops, economically and as a way to mitigate GHG emissions. Continue reading

Life Cycle Inventory of Electricity Cogeneration from Bagasse in the South African Sugar Industry

by Monkgogi Bonolo Otohogile

South Africa’s sugar industry is worth over $1.11 billion and South Africa is consistently ranked as one of the top 15 sugar producing countries in the world. The sugar manufacturing process also produces thousands of tonnes of a biomass called bagasse that is being underutilized. Mashoko et al. (2013) investigated the potential for the cogeneration of steam and electricity using bagasse in South Africa’s sugar industry. The authors’ developed life cycle inventories for bagasse electricity production, which they used to evaluate the environmental impacts of cogeneration. Using data supplied by various affiliated organizations and studies, Mashoko and colleagues determined the greenhouse gases, energy ratio, non-renewable energy input, sulfur dioxide, and nitrogen dioxide of a functional unit of 1 GWh of bagasse-derived electricity produced in the South African sugar industry and compared it to coal-derived electricity and bagasse-derived electricity in Mauritius. The authors found that bagasse-derived electricity performed better than coal-derived electricity in every category outlined above. Mashoko et al. argued that by increasing their boiler pressure, the sugar industry could produce cleaner electricity during the sugar life cycle by following in the footsteps of Mauritius. Bagasse-derived electricity could mitigate South Africa’s massive carbon dioxide emissions while also making the sugar industry self-sufficient and contributing to the grid. Continue reading

Sustainable Bioenergy: Evolving Stakeholder Interests

by Christina Whalen

The diversity of stakeholders’ interest and values complicates the decision-making process involved in the future of sustainable bioenergy production. Johnson et al. explores the different stakeholder perspectives and then examines how this diversity affects research on the subject. Biofuel production has been brought to the public’s attention because of the need to mitigate greenhouse gas (GHG) emissions, increase energy security, support farm production, and improve economic growth in rural areas. The recent increase in biofuel consumption has resulted in stakeholders questioning environmental, economic, and social benefits of using agriculture to produce ethanol and biodiesel. As a result, policy makers have passed legislation and modified regulations about renewable fuel production in order to promote the use of alternative biomass feedstocks. The general research community is looking for ways to convert this feedstock to a usable fuel source in vehicles. The expansion of biofuel production coincides with Continue reading