In Tacoma, Washington, the city collects all food waste for composting throughout the city, (in large bins near regular waste). On the other hand, citizens can get nutritious soil, wonderful fertilizers for their gardens and fruit trees. Side stories, gentle visitors coming for apples in the yards, born of trash. Image by CleanTechnica.

The expected decline in landfill numbers across the United States along with bans on dumping large amounts of organic waste in landfills that have been approved in many states has prompted researchers at the U.S. Department of Energy’s National Renewable Energy Laboratory ( DOE) (NREL) to consider other ways to deal with the issue of food waste disposal.

The researchers concluded that there is no single solution in the United States for treating food waste dumping. NREL researchers Alex Badgett and Anelia Milbrandt came to that conclusion after examining the economics involved in five different ways to tackle food waste dumping, including dumping it in a landfill. Both researchers are part of the NREL Strategic Center for Energy Analysis.

“If we are trying to develop an optimized waste management system in the US that diverts all food waste from landfills, there is not necessarily any technology that will work for all areas of the country,” Badgett said. “An optimized system is likely to use different technologies in different countries and in different sizes.”

Badgett and Milbrandt co-authored a recently published paper entitled “Disposal and Utilization of Food Waste in the United States: A Spatial Benefit Analysis,” which appears in Cleaner Production Newspaper.

About 75% of food waste ends up in landfills. But many landfills are moving close to capacity and a significant number are scheduled to close by 2050, the researchers found. Although ample land is available for new landfills in rural America, residents in more populated regions will be forced to transport waste over long distances for disposal. Second, organic waste disposal bans approved in some states require the disposal of food waste in facilities other than landfills. Given the need for investment in new waste management facilities, there is an opportunity for innovative and improved waste flow routes. Badgett and Milbrandt considered five options for what to do with food waste, including continuous dumping. The other four options are:

  • Anaerobic digestion, in which microorganisms break down biodegradable material in the absence of oxygen
  • Composting, a biological process involving the decomposition of organic matter in a controlled environment to produce compost
  • Combustion, where garbage is burned for heat and / or energy
  • Hydrothermal liquefaction, in which wet organic material is converted into biocrude.

The burning has gone out of favor due to increased environmental regulations and public opposition to the construction of new facilities. Hydrothermal liquefaction remains in the pilot phase.

The researchers examined the operating economics of different types of equipment, taking into account how much revenue each of the users brings or from selling the products. They modeled the financial viability of technologies, taking into account the capital and operating costs of equipment; revenues from the sale of energy, heat, fuels and other products; and production credits such as Renewable Identification Number (RIN) credits under the Renewable Fuel Standard for the production and use of biogas as vehicle fuel.

All ways to treat food waste exhibit some economies of scale (where costs are reduced when facilities are built to a larger size), but the researchers found that the extent to which financial viability varies with facility size is inconsistent. For example, landfills and incinerators set up to treat municipal solid waste, including food waste, need to be built in large sizes in order to take advantage of economies of scale for these roads, while solvents and composters can be built in scale. smaller and still provide a profitable alternative to food waste disposal.

All different types of equipment would benefit from the development of technologies to produce biogas or similar products, but the benefits are greater for those operating on a medium to large scale. Facilities that currently accept food waste in large quantities are more suitable to maximize the economic benefits associated with the production of fuels, energy or products as they have a supply of ready-made raw materials available.

Waste management facilities charge users a port fee to offset operating and capital costs. If a facility can produce enough biogas to reduce its tariff dependence, it either becomes more profitable or it can lower those tariffs to become more competitive.

The location of a structure plays an important role in determining its benefit, the researchers found. For example, states along the East and West coasts have the highest gate tariffs and are therefore more economically advantageous.

The DOE Bioenergy Technology Office funded the research.

NREL is the US Department of Energy’s leading national laboratory for research and development of renewable energy and energy efficiency. NREL is operated for the Department of Energy by the Sustainable Energy Alliance, LLC.

Courtesy of NREL, US Department of Energy.

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