ACT 101: What is Waste-to-Energy?

December 5, 2019

ACT 101 is a series of articles breaking down the basics of clean fuels, transportation technologies, funding programs, and other emerging trends.

Waste-to-energy (WTE) is the commercially-proven process of recovering energy from municipal solid waste (MSW) for power production. MSW consists of biomass, or biogenic (plant or animal products), paper, cardboard, food waste, grass clippings, leaves, wood and leather products, glass, metals, and nonbiomass combustible materials such as plastics and other synthetic materials made from petroleum. Waste is a resource for the WTE process.

The need for advanced waste management solutions has never been greater. Statistics on waste production and recycling in the US venture on dismal. As of 2017, the US generated 267.8 million tons of MSW (about 4.51 pounds per person per day). This represents an increase of almost six million tons from 2015 figures. Even after recycling, over 50% of MSW is still landfilled. Only 12-13 % of total MSW generated goes to waste-to-energy processes.

Landfills produce high levels of the greenhouse gas methane as well as leachate, the toxic liquid byproduct that percolates from landfills and can pollute groundwater. Methane is a less talked about, but powerful, greenhouse gas that has 84 times the global warming potential of carbon dioxide in the first twenty years after its release. Landfill methane alone is the third largest source of emissions in the US and a major factor contributing to climate change.

Landfill methane alone is the third largest source of emissions in the US and a major factor contributing to climate change.

Complicating US recycling matters more, China’s recent National Sword decision (announced in 2017 and enforced early 2018) to stop accepting overseas plastic waste imports has also greatly impacted US waste stream processes. The US previously sent China about 40% of its recyclables, but China’s abrupt decision to stop accepting overseas plastic waste has greatly impacted municipal recycling rates and even resulted in a shutdown of recycling centers around the country.

The reverberating effects of this one sudden policy change reiterates the fact that recycling is no longer the solution to our waste problem—in fact, it never was. The massive waste challenge we are currently presented with, however, also represents a huge opportunity to transform MSW, a previously untapped resource, into usable energy.

How is Energy Recovered in Waste-to-Energy?

Incineration

WTE processes include incineration, gasification, pyrolization, and anaerobic digestion. Incineration is one of the most common WTE processes and involves burning waste to create steam. The steam turns a turbine and generates electricity and heat which could then be used for district heating or cooling.

Waste-to-energy plants tend to be large in scale to accommodate the necessary processes involved. The incineration process creates byproducts such as fly ash, a waste product that goes to landfill after ferrous metals and toxins have been removed.

Anaerobic Digestion

Anaerobic digestion produces a biogas which is then converted to ultra-low-carbon RNG.

Anaerobic digestion is another form of waste-to-energy. It is the process of breaking down organic material, including agricultural waste from land farms and dairy waste, food waste, and waste from wastewater treatment plants, to produce energy. Anaerobic digestion produces a biogas (comprised mostly of methane and carbon dioxide) which is then converted to ultra-low-carbon renewable natural gas (RNG). Once cleaned and processed, RNG can be injected directly into the existing natural gas pipeline to be used for commercial and residential heat and power or delivered to natural gas filling stations and used as a transportation fuel.

Depending on the original feedstock, for instance dairy waste, RNG is even considered a carbon-negative fuel. Because RNG utilizes methane captured from organic sources that would otherwise escape into the atmosphere, RNG takes more carbon out of the environment than it produces.

Investing in Waste-to-Energy at Scale

Waste collection company CR&R’s anaerobic digestion facility produces 4 million gallons of RNG annually.

Companies across the US are investing in anaerobic digestion to turn waste streams into viable energy resources. One of the first companies to introduce three-crate curbside recycling program in 1986 that revolutionized at-home recycling, waste and recycling collection company CR&R Environmental Services continues to innovate and explore alternatives to landfill.
Driven by ambitious goals of 0% landfill, 0% fossil fuels, 100% resource conservation, and 100% renewable fuels, CR&R’s state-of-the-art anaerobic digestion facility in Perris, California produces 4 million gallons of RNG annually, which in turn fuel CR&R’s own fleet of vehicles, as well as organic fertilizer and soil products for landscaping.

WTE’s Local and International Profile

The WTE strategy has been slow to expand in the US. A large amount of land available for waste disposal coupled with no significant regulatory mechanisms in place to discourage using land for landfills, has been one major contributing factor to the slower adoption of WTE projects.

However, WTE projects have gained traction in Europe and in Asia due to land and space considerations. The waste management conglomerate Covanta currently has over 40 WTE plants in North America and Europe combined. In China, the Shenzhen East Waste-to-Energy Power Plant in Shenzhen, planned to be operational in 2020, is designed to incinerate 5,000 tons of waste per day to generate 550,000 MWh annually—enough to power about 50,000 average American homes per year.

Newer research is helping the public reconsider WTE as a much-needed energy recovery and waste management strategy.

Persistent Barriers and Promising Solutions

Though WTE can be considered a carbon-negative solution to both waste and landfill management, it has experienced its share of criticisms. Environmental justice concerns have stalled past projects over issues surrounding pollution from mercury, lead, dioxins (persistent organic pollutants), methane, and furans (carcinogenic organic compounds), as well as perception of pollution from local communities.

Though the federal Clean Air Act amendments of 1990 have resulted in cleaner WTE technologies, incineration plants still evoke negative images of pollution and public opposition to such projects understandably follows suit. Public education surrounding the technologies has not adequately addressed the technological advancements that have improved efficiency and pollutant concerns. However, newer research is helping the public revisit the concept of the polluting WTE plant and reconsider WTE as a much-needed energy recovery and waste management strategy.

A Viable Energy and Waste Solution

WTE remains a viable, commercially scalable energy production strategy that can address multiple waste management, energy generation, and environmental issues with appropriate facility pollution controls in place.

Though the initial expense to build a WTE project can be significant, some initial costs can be offset through state and federal grant programs. WTE facilities also provide a long-term revenue stream for cities and businesses by way of power and energy sales. As the public puts more pressure on governments to act on behalf of climate and health concerns, WTE can, and should, be incorporated into power source generation portfolios.

While WTE plants alone may not generate the electricity and power needed to sustain national or state energy requirements, they must be strongly considered given our current waste generation profiles. Support from local communities, investment from government, and better education initiatives are critical to not only dispel myths about the impacts of WTE project but convey the benefits as well.