This is an edited version of an email exchange between Mr. Steve Bratkovich of Dovetail Partners Inc., Professor Nickolas Themelis of Global WTERT Council (GWC) and Nora Goldstein of BioCycle Magazine.
Subject: Differences in wood waste and municipal solid waste (MSW) numbers published by the US EPA as Municipal Solid Waste in the United States: Facts and Figures, and the State of Garbage, a bi-annual survey conducted by Columbia University and Biocycle Magazine.
Mr. Bratkovich: The differences you found in MSW generation and management between the EPA/Franklin studies and your study is quite interesting. Also, as someone (a professional forester) engaged in the literature review of this topic I've noticed most forestry-types tend to cite the EPA numbers;
Do you (Columbia or BioCycle) have numbers that break out the wood portion of your study similar to the EPA studies?
Prof. Themelis (for Columbia Univ.): No, we do not.
Nora Goldstein (for BioCycle): We do not have a more detailed breakdown of wood waste in the MSW stream. One thing we've noted in BioCycle articles is how much woody debris is generated by the severe weather events so many parts of the country have been experiencing in recent years. This can skew numbers, more at the local level, versus the national aggregated numbers.
Mr. Bratkovich: The US EPA (2010) estimates that "wood" comprises 15.88 million tons (generation) out of approx. 249 million tons of MSW. Of this 15.88 million tons, the EPA notes that 2.30 million tons were recovered, resulting in a 14.5% recovery.
Prof. Themelis: The EPA tonnages of recovery of various materials are reliable because they get them from numbers of industry associations, e.g. paper recycling companies. However, their numbers of tonnages of MSW landfilled are not (reliable) because they are not based on recorded tonnages of MSW landfilled, as the Biocycle/Columbia study does.
The 15.9 mill tons most likely were calculated by multiplying 249 x 6.4%. The 6.4% sounds reasonable. An EPA study in 1997 (EPA 530-s-97-015) had estimated 7% wood in typical msw ;
Mr. Bratkovich: Your numbers are much higher for total generation (about 390 million tons). Is it safe to assume your "wood" component recovery is proportional to EPA numbers?
Prof. Themelis: Not at all.
Mr. Bratkovich: Also, EPA divides up their "wood" portion between durable goods and wood contained in containers and packaging (like pallets). Any similar division with your data?
Prof. Themelis: We have no information on this subject because we have not studied it. Go to WTERT's SOFOS Database and search for C & D (construction and demolition) recycling to see what we know. The problem with wood in msw is that wood can be of different kinds, Eg: tree stumps, branches, chemically treated wood, wood chips/residues, that's why estimates of wood in MSW vary widely from the 7% of EPA down to 2% in Tchobanoglous 's Handbook and in SCS survey of New York City's waste in the 90s.
Mr. Bratkovich: And finally, any sense how much of your combustion to energy includes wood (e.g., pallets)?
Prof. Themelis: I would say a total of 5% of the msw combusted for electricity production in the United States, i.e. about 1.5 million tons. The wood that is mixed in MSW is by-and-large non-usable except for energy recovery. Wood pallets, C & D, and usable wood from furniture, all source separated, are the only candidates for material recovery from used wood. The only other possibilities are energy recovery by combustion of wood processing residues in dedicated boilers - a lot of that is done already - or increasing the existing United States' Waste-to-Energy (WTE) capacity.
Subject: Differences in wood waste and municipal solid waste (MSW) numbers published by the US EPA as Municipal Solid Waste in the United States: Facts and Figures, and the State of Garbage, a bi-annual survey conducted by Columbia University and Biocycle Magazine.
Mr. Bratkovich: The differences you found in MSW generation and management between the EPA/Franklin studies and your study is quite interesting. Also, as someone (a professional forester) engaged in the literature review of this topic I've noticed most forestry-types tend to cite the EPA numbers;
Do you (Columbia or BioCycle) have numbers that break out the wood portion of your study similar to the EPA studies?
Prof. Themelis (for Columbia Univ.): No, we do not.
Nora Goldstein (for BioCycle): We do not have a more detailed breakdown of wood waste in the MSW stream. One thing we've noted in BioCycle articles is how much woody debris is generated by the severe weather events so many parts of the country have been experiencing in recent years. This can skew numbers, more at the local level, versus the national aggregated numbers.
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| US EPA's cartoon for their report: Characaterization of Municipal Solid Waste in the United States: 1996 Update |
Mr. Bratkovich: The US EPA (2010) estimates that "wood" comprises 15.88 million tons (generation) out of approx. 249 million tons of MSW. Of this 15.88 million tons, the EPA notes that 2.30 million tons were recovered, resulting in a 14.5% recovery.
Prof. Themelis: The EPA tonnages of recovery of various materials are reliable because they get them from numbers of industry associations, e.g. paper recycling companies. However, their numbers of tonnages of MSW landfilled are not (reliable) because they are not based on recorded tonnages of MSW landfilled, as the Biocycle/Columbia study does.
The 15.9 mill tons most likely were calculated by multiplying 249 x 6.4%. The 6.4% sounds reasonable. An EPA study in 1997 (EPA 530-s-97-015) had estimated 7% wood in typical msw ;
Mr. Bratkovich: Your numbers are much higher for total generation (about 390 million tons). Is it safe to assume your "wood" component recovery is proportional to EPA numbers?
Prof. Themelis: Not at all.
Mr. Bratkovich: Also, EPA divides up their "wood" portion between durable goods and wood contained in containers and packaging (like pallets). Any similar division with your data?
Prof. Themelis: We have no information on this subject because we have not studied it. Go to WTERT's SOFOS Database and search for C & D (construction and demolition) recycling to see what we know. The problem with wood in msw is that wood can be of different kinds, Eg: tree stumps, branches, chemically treated wood, wood chips/residues, that's why estimates of wood in MSW vary widely from the 7% of EPA down to 2% in Tchobanoglous 's Handbook and in SCS survey of New York City's waste in the 90s.
Mr. Bratkovich: And finally, any sense how much of your combustion to energy includes wood (e.g., pallets)?
Prof. Themelis: I would say a total of 5% of the msw combusted for electricity production in the United States, i.e. about 1.5 million tons. The wood that is mixed in MSW is by-and-large non-usable except for energy recovery. Wood pallets, C & D, and usable wood from furniture, all source separated, are the only candidates for material recovery from used wood. The only other possibilities are energy recovery by combustion of wood processing residues in dedicated boilers - a lot of that is done already - or increasing the existing United States' Waste-to-Energy (WTE) capacity.
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