Biofuels and Bioproducts from Wet and Gaseous Waste Streams: Challenges and Opportunities

Abstract

Historically, the concept of "waste-to-energy" has referred to any of a number of highly mature technologies (e.g. incineration or anaerobic digestion) that decrease waste volumes. Landfill capacity scarcity, coupled with increasingly stringent disposal regulations, is necessitating novel waste management solutions. In particular, the notion that waste streams represent valuable feedstocks for the production of biofuels and bioproducts is gaining currency. These feedstocks include inedible fats and greases, biogas from landfills, dairies, wastewater treatment plants, and the organic fraction of municipal solid wastes. Conversion of these feedstocks into renewable natural gas, diesel, and aviation fuels is just beginning to gain market traction. It represents a significant opportunity for additional expansion.Terrestrial feedstocks are currently the largest resource generated for the bioeconomy, estimated at 572 million dry tons for 2017 (Billion Ton 2016), and have traditionally constituted the primary focus of the Bioenergy Technologies Office (BETO). However, the resource assessment conducted by the National Renewable Energy Lab and Pacific Northwest National Lab indicates that wet waste feedstocks (Summarized in Table ES-1) could also make significant contributions to the bioeconomy and domestic energy security goals.

Anaerobic biodegradation of brown grease and its potential as a source of renewable energy

“…Regardless, 0.04 g COD/g VS. day substrate utilization rate at the highest BG loading translates into 0.8 kg COD/m 3 day volumetric loading rate for typical low rate anaerobic processes, which are operated at 2% VS content. Considering the fact that typical low rate anaerobic processes with complete mixing are designed for 1-2 kg COD/m 3 day loading rates for easily biodegradable soluble COD containing wastes (Totzke, 2017), 0.8 kg COD/m 3 . day for BG is very encouraging.…”

“…It is also a proven and effective process for pretreatment of high strength industrial wastewaters. The process provides the additional benefit of creating an opportunity to utilize methane (CH 4 ), the main product of anaerobic digestion, as a renewable energy source (McCarty et al, 2011;Totzke, 2017).…”

Pilot-Scale Continuous Plug-Flow Hydrothermal Liquefaction of Food Waste for Biocrude Production

“…Evidently, food waste biochemical compositions vary largely with their sources. 1 Both feedstocks had low ash contents (5.71−7.15%), which helped to prevent charring upon heating in the reactor.…”

“…The United States produces 77 million dry tons of biowaste annually from the food system alone. 1 This biowaste has been treated as a burden bearing a negative cost. On the other hand, these waste streams have a high content of energy and nutrients that can be recovered and reused.…”

Will Membranes Break Barriers on Volatile Fatty Acid Recovery from Anaerobic Digestion?

“…The conversion of organic wet waste materials such as wastewater sludge, food waste, animal waste, and fats, oils, and greases (FOG) into valuable fuels and chemicals provides a sustainable pathway toward reducing fossil fuel consumption and waste valorization. The U.S. Department of Energy estimated that 50 million dry tons of combined wet organic wastes are available each year in the United States for conversion to biofuels, bioproducts, or biopower, which represents an untapped energy potential of nearly 0.6 quadrillion British thermal units (Btu) . Anaerobic digestion (AD) is a widely used technology that transforms organic waste into CH 4 -rich biogas. , However, the low economic value of biogas and the additional costs associated with its cleanup and upgrading make investment in AD difficult without extensive government subsidies. − …”