Life-cycle energy and climate benefits of energy recovery from wastes and biomass residues in the United States

Abstract

A t the beginning of the new millennium, energy insecurity, global climate change and stagnant rural economies led to policies supporting domestic biofuels as a renewable alternative fuel in more than 60 countries worldwide 1. As a consequence, global production of ethanol and biodiesel combined almost quadrupled (from about 35 billion litres to 135 billion litres) in the short span from 2005 to 2016 (ref. 2). However, these policies had two major flaws. First, appropriation of edible crops for biofuel (mainly corn and sugarcane for ethanol, and soybean, canola and palm for biodiesel) was an important factor responsible for food price inflation alongside other factors such as rising income that drove rapid growth in food demand (especially meat demand), rising energy prices, adverse weather shocks, currency fluctuations and trade policies 1,3-6 , the consequences of which were particularly severe for poorer households in developing countries 7. Second, these crops required intensive use of land, water, nitrogen and other farm chemicals, which meant low, and in the worst case uncertain, net environmental benefits 8-12. Being widely available and replenishable, wastes and biomass residues from agricultural, dairy, forestry and household activities seem to contain the basic attributes of a sustainable energy resource, in stark contrast to bioenergy from food crops 13-15. The US Department of Energy 2016 Billion-Ton Study estimates an annual availability of 233 million tonnes (Mt) of dry waste 16. To put this in perspective, the approximately 60 billion litres of corn ethanol produced in the United States in 2017 required about 150 Mt of corn (assuming a yield of 402 l ethanol per Mt). Furthermore, wastes and biomass residues can be used to derive a number of alternative energy products, including electricity along with heat, biomethane (or renewable natural gas), ethanol, renewable diesel or bio jet fuel, each through various conversion pathways, which currently are at different stages of technical and economic maturity 14,15,17-21. Beyond energy production and mitigation of climate change, efficient use of wastes and residues is integral to the achievement of sustainable development 22 , and to redesigning our economies to minimize

Spatial distribution of usable biomass feedstock and technical bioenergy potential in China

“…Although the conversion technology and energy conversion coefficients would change heavily in the future, some assumptions are made based on the conversion technology trends and the actual utilization at present as follows: (a) electricity and heat, biogas, and bioethanol are three kinds of final bioenergy in this research. (b) According to the public preferences and climate benefit research of energy recovery from wastes and biomass residues (Liu & Rajagopal, ; Zhao, Cai, Li, & Ma, ), thermal combustion through biomass‐assisted heat and power plants is the optimal pathway for woodland and agricultural residues, and thermal combustion is therefore adopted for all the residues in this research. (c) According to the actual utilization of waste at present (National Bureau of Statistics, ; ), all the municipal sewage sludge and animal manure are used for biogas production via anaerobic digestion while considering the process of cleaning and compression, half of the municipal waste is converted into biogas via anaerobic digestion, and the rest of the municipal waste is used for thermal combustion.…”

Waste Recovery through Thermochemical Conversion Technologies: A Case Study with Several Portuguese Agroforestry By-Products

“…In this way, when other supply chains are created, competition between traditional industries is avoided, such as pulp and paper or the production of wood pellets, with the production of energy [49][50][51]. This non-competition allows, first, the use of resources that until now have not been used, and therefore, with low market value, its cost depending only on the complexity of its supply chain; and, second, the creation of a truly sustainable option, in a perspective of circular economy, where all resources are valued, to the detriment of the intensive exploitation of forest resources [52][53][54].…”

Bioenergy from biofuel residues and waste

“…Liu and Rajagopal (2019) use life‐cycle assessment to evaluate the potential of agricultural and forestry residues, municipal solid waste, and animal manure to generate renewable energy within the United States. They found that the utilization of these available wastes and residues could deliver 2.4–3.2 EJ of net energy gain and displace 103–178 million tons of CO 2 ‐equivalent of greenhouse gas emissions.…”