If the U.S. recovered the energy from its non-recycled plastic by converting these materials into fuel, it could generate enough for the equivalent of 6 million cars annually. That finding released by the American Chemistry Council from a study conducted for it by 4R Sustainability Inc. on increasing opportunities for plastics-to-fuel "conversion technologies".
The ACC said recapturing such waste plastic would help to create a "reliable source of alternative energy from an abundant, no-cost feedstock" while diverting potentially valuable material from landfills. The report found that many of these plastic-to-fuel conversion technologies are already being implemented on a commercial scale in Europe and Asia.
Citing 2007 LA county data, the study cited five companies offering anaerobic digestion, thermal depolymerization, pyrolysis, and high- and low-temperature gasification. The throughputs for the technologies from Arrow Ecology and Engineering, Changing World Technologies, International Environmental Solutions, Interstate Waste Technologies, and NTech Environmental range in outputs from 125 to 935 tons/day.
Fuel yields and production costs will vary based the nature of the feedstock and regional labor and energy costs but as a general example the report found that:
- One ton of mixed scrap plastic = 264 gallons of consumer-ready fuel
- Production costs (if plastic is free) = $0.75 per gallon
As for the business model, benefits could be derived from either the sale of the fuel product, or the offsetting of fuel costs if a company uses the fuel internally. PTF-derived fuel is reportedly competitive to traditionally-derived fuel, even if the price of crude oil drops to about $40 per barrel.
In terms of maximizing the inherent energy of plastics, pyrolysis seems to be a better option than incineration with energy recovery. Using the same formula for estimated production numbers, 5.6 lb of scrap plastic would produce one gallon of diesel fuel. In terms of energy values:
- One gallon of oil = 138,095 BTU
- One pound of mixed plastic = 15,500 BTUs (when incinerated)
Based on the calculation, one ton of scrap plastics would produce 264 gallons of consumer-ready fuel, with about 7.57 lb of plastic to make one gallon of fuel.
The BTU value of 7.57 lb of plastic when incinerated would be about 117,424 BTUs. "Compare that to the 138,095 BTU value of diesel, which also requires 7.57 pounds of plastic, and these calculations suggest that PTF yields better energy value from scrap plastics," the report stated. Also to be considered is the BTU value of the so-called "char residual" left over from the process.
The ACC also released a series of cases studies examining waste-to-energy (WTE) facilities, finding that currently in the U.S., there are 86 WTE facilities that process nearly 30 million tons of solid waste annually, recovering enough energy to power 2 million homes. That's enough to save the equivalent of 30 million barrels of oil and prevent the release of 40 million tons of greenhouse gas emissions annually.
According to the U.S. Environmental Protection Agency, the United States currently recovers the energy from about 14% of waste through WTE facilities. But these technologies are more prevalent in Japan and Europe, which use WTE to recover energy from 75% and 40% of municipal solid waste, respectively.