As a pure waste-to-energy technology, the TVRC competes with mass burn incinerators, anaerobic digesters as well as traditional gasification systems within the MSW marketplace. While mass burn incinerators are the most popular still to this day, they generate significant amounts of fly ash, which in the near term could become even more expensive to treat as in June 2010, the US EPA started to consider classifying fly ash (CCRs) as a hazardous waste. Should this be the final directive, it will significantly impact how fly ash is ultimately handled.
While MSW applications have started to emerge using gasification, it is important to note that a significant amount of sorting and pre-treatment is required in order to make the feedstock more uniform in nature to maintain the steady flow and composition of the syngas generated. Additionally, the TVRC generates electricity at a much lower cost.
||Capital Cost per MW
||~ $5+ MM/MW
||~ $3+ MM/MW
|Mass burn (waterwell/modular/RDF boiler/fluidized bed)
||~ $2+ MM/MW
Finally, the TVRC generates significantly more electricity per ton of MSW versus some of the emerging technologies. Referencing back to one of the aforementioned proposed plasma gasification and plasma arc projects in Florida, the $120 million 600 TPD system was marketed to generate about 42 MW, of which only 18 MW would be sold to the grid.
A TVRC waste-to-energy & waste to resource system also represents the most efficient land usage when compared to other renewable energy options.
||Land per MW
Many contest that the primary goals for waste management; to reduce, reuse and recycle, and increasing waste conversion (i.e. waste-to-energy) rates are not compatible. However, in the United States, the states making the most use of waste-to-energy facilities are also those that recycle the most.
In addition, according to a recent study conducted by the EPA, increasing recycling wastes actually improves the efficiency of waste conversion (i.e. waste-to-energy).
Consumers are increasingly recycling more biogenic waste (paper and food) and throwing away more non-biogenic waste (rubber and plastics).
The higher energy content of non-biogenic waste makes it a more productive feedstock for generating electricity through a waste-to-energy technology such as the TVRC. Conversely to previously held views then, recycling is not just compatible with waste conversion, it actually improves the energy content of the leftover waste, boosting the potential of key waste-to-energy technologies, including plasma-arc plasma gasification.
According to the US EPA, in 2010 the US produced almost 250 million tons of municipal solid waste (MSW), of which only 12% was diverted towards waste-conversion (example: waste to energy) facilities. This generated approximately 14 million megawatt hours of electricity.
Landfilling is still the largest single means of trash disposal as more than half of all MSW produced in the US was sent to landfill in 2011 (The average American produces 4.4 pounds of waste per day with landfill diversion targets becoming more widespread and stringent). Diverting waste from a landfill to generate value from it is in itself a compelling reason to invest in waste conversion and/or waste to energy, however it also reduces greenhouse gas emissions.
In 2009, 17% of all human-related methane emissions in the US came from landfills. Further, the scarcity of land around urbanized areas means some municipalities are forced to transport waste long distances for disposal. For example, New York’s Department of Sanitation spends in excess of $300 million per year moving waste by truck to landfill and waste disposal facilities outside of the city.
PEAT’s TVRC is an innovative waste to energy technology that combines a thermal volume reduction (“TVR”) system on the front end with a core plasma-arc, plasma gasification PTDR system on the back-end for ash treatment. This combination maximizes electricity generation and minimizes residual by-product treatment.
Finally, in 2007, the EPA stated that waste to energy facilities comply with stringent air emissions standards and produce electricity with less environmental impact than almost any other source of electricity.
All of the high temperature boiler/reactors – a key component of the TVRC technology – installed and operating to date required an air permit from the applicable regulatory body. Typically, these systems are designed to comply with emissions levels for particulate matter (150 μg/m3), NOx (0.04 PPMV), SOx (0.03 PPMV) and carbon monoxide (9 PPMV), as well as the other typical reference pollutants as they pertain to air emissions.
Below is a summary of the most recent third party emissions testing conducted on a recently commissioned PTDR plasma-arc, plasma gasification. The test was conducted for medical waste treatment. The summary also compares the results to current United States air emission regulations.
|USA – EPA
40 CFR Part 60
Standards of Performance for Stationary Sources and Emission Guidelines for New Sources: HMIWI
Taiwan – EPA
(corrected to 7% oxygen as per US EPA standards)
||N.D. (D.L. 1.5mg/m3)
||N.D. (D.L. 1μg/m3)
||N.D. (D.L. 1μg/m3)
|Dioxins & Furans
||2.3 ng TEQ/dscm
||0.1 ng TEQ/dscm
The following parameters were also tested but were found to be non detectible (Detectible limit in parentheses) Chlorides as Cl (1.4 mg/m3), Ammonia (5 mg/m3), Hydrogen Sulfide (1.4 mg/m3). With regards to Volatile Organic Compounds (VOCs), the testing for Benzene, Ethyl Benzene, Toluene and Xylene were all below the detectible limit (1 mg/m3). Finally, with regards to heavy metals with the exception of cadmium, which is listed above, all were below the detectible limit of 1 μg/m3 (antimony had a detectible limit of 5 μg/m3).
It is worth noting that the above emissions for the PTDR plasma-arc, plasma gasification were measured when the energy recovery system (gas engine was not operating and thus the syngas was thermally oxidized. It is noted that if the syngas is utilized in a gas engine or other syngas utilization equipment, then the only gas emissions associated with the PTDR plasma-arc, plasma gasification system would be the exhaust from that source.
According to the United States Environmental Protection Agency’s “Solid Waste Management and Greenhouse Gases: A Lifecycle Assessment of Emissions and Sinks”, disposing of 650,000 tons per year in a landfill without gas collection, could reduce its Greenhouse Gas (GHG) emissions by about 260,000 Metric Tons Carbon Equivalent (MTCE) per year by managing waste in a mass burn combustor unit. For this preliminary discussion, this equates to 0.40 MTCE/ton avoided from landfilling.
However, the EPA’s document uses a combustion system efficiency of 550 kWh per ton of mixed MSW. The high temperature boiler/reactor system in the TVRC system, which combines a high temperature boiler/reactor with a plasma-arc, plasma gasification sytem, has an efficiency of approximately 690 kWh per ton – 25% greater efficiency; thus the high temperature boiler/reactor has the potential to generate approximately 0.50 MTCE/ton avoided from landfilling or in total up to 82,500 MTCE, when assuming 500 TPD.
Additionally, the EPA estimates greenhouse gas (GHG) emissions range from 10 to 20 million metric tons, depending on the different methods used to estimate the biogenic fraction of MSW. EPA’s eGrid (a database of information on electrical generators in the United States) indicates about 53% of the energy generated by MSW combustion facilities is from biogenic sources and 47% is fossil-fuel derived power. If we take that 53% and presume the same percent of GHG emissions are from biogenic sources, then MSW combustion facilities generate less GHGs than fossil-fuels.
||CO2 (lbs per MWh)
EPA estimates the GHG savings from WTE to be about 1 on of GHGs saved per ton of MSW combusted.