Biofuels - Both biodiesel and renewable diesel can be produced from plant or animal oils, fats, and wastes. According to the U.S. Energy Information Administration, the United States uses a combination of oils and fats in biodiesel production: soy oil 65%, corn oil 7.5%, and yellow grease and white grease was less than 8% of production of 8,478 million pounds of feedstock inputs for biodiesel in 2013. According to the latest published life-cycle analysis for various feedstocks and the feedstock mix reported by the Energy Information Administration and the U.S. EPA for 2013, the average GHG reduction for biomass-based diesel exceeds 80%. If biofuels provided a quarter of transport fuel in 2050, it would avoid an estimated 2.1 gigatons of GHG emissions per year. Although biofuels are among the few fuels for medium- and heavy-duty trucking that are considered renewable, there are some issues regarding its status as a sustainable fuel source. The sustainability of biofuels comes into quest
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The major sources of feedstock (raw material) for making biodiesel in the United States and their shares of total biodiesel feedstocks in 2017 were
Soybean oil—52%
Canola oil—13%
Corn oil—13%
Recycled feedstocks, such as used cooking oils and yellow grease—12%
Animal fats—10%
Rapeseed oil, sunflower oil, and palm oil are major feedstocks for biodiesel produced in other countries.
Biodiesel is most often blended with petroleum diesel in ratios of 2% (referred to as B2), 5% (B5), or 20% (B20). Biodiesel can also be used as pure biodiesel (B100). Biodiesel fuels can be used in regular diesel engines without making any changes to the engines. Biodiesel blends are also used as heating oil. Biodiesel can be stored and transported using petroleum diesel fuel tanks and equipment.
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The operation of wastewater treatment plants results in direct emissions, from the biological processes, of greenhouse gases (GHG) such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), as well as indirect emissions resulting from energy generation. In this study, three possible ways to reduce these emissions are discussed and analyzed: minimization through the change of operational conditions, treatment of the gaseous streams, and prevention by applying new configurations and processes to remove both organic matter and pollutants. In current WWTPs, to modify the operational conditions of existing units reveals itself as possibly the most economical way to decrease N2O and CO2 emissions without deterioration of effluent quality. Nowadays the treatment of the gaseous streams containing the GHG seems to be a not suitable option due to the high capital costs of systems involved to capture and clean them. The change of WWTP configuration by using microalgae or partial nitritation-Anammox processes to remove ammonia from wastewater, instead of conventional nitrification-denitrification processes, can significantly reduce the GHG emissions and the energy consumed. However, the area required in the case of microalgae systems and the current lack of information about stability of partial nitritation-Anammox processes operating in the main stream of the WWTP are factors to be considered.