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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Bioproducts Research » Research » Publications at this Location » Publication #343737

Research Project: Technologies for Improving Industrial Biorefineries that Produce Marketable Biobased Products

Location: Bioproducts Research

Title: A pilot-scale steam autoclave system for treating municipal solid waste for recovery of renewable organic content: Operational results and energy usage

Author
item Holtman, Kevin
item Bozzi, David
item Franquivillanueva, Diana
item Offeman, Richard
item Orts, William - Bill

Submitted to: Waste Management and Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/17/2016
Publication Date: 3/17/2016
Citation: Holtman, K.M., Bozzi, D.V., Franqui-Villanueva, D.M., Offeman, R.D., Orts, W.J. 2016. A pilot-scale steam autoclave system for treating municipal solid waste for recovery of renewable organic content: Operational results and energy usage. Waste Management and Research. 34(5):457-464. doi: 10.1177/0734242x16636677.

Interpretive Summary: Municipal solid waste (MSW) could potentially be a significant feedstock resource for creating bioenergy; however, it is often seen as too complex and too variable. Steam autoclaving of solid wastes has long been used to sterilize medical wastes, but it was used here on more traditional MSW to create uniform and predictable feedstocks for biofuels production. In this study, MSW was treated in a pilot-scale (1800 kg per batch capacity) autoclave that converts MSW into a uniform pulp product by steam treatment at 120C for at least 20 minutes. The resulting pulp from autoclaved MSW was then efficiently separated into its renewable organic content and non-renewable organic content fractions via size-screening. This study provides evaluation of autoclave operation at an actual landfill site, including mass and energy balances for the purpose of integration into a commercial-scale, organic diversion system. Several methods of MSW treatment were explored, including (1) indirect oil heating only, (2) a combination of oil and direct steam during the same cooking cycle, and (3) steam treatment only. Gross energy requirements averaged 1290kJ per kilogram of material in the vessel, including the weight of free water and steam added during heating. On average, steam recovery can recoup 43% of the water added and 30% of the energy, supplying 40% of the steam requirement to start the next batch in an adjacent system. Discussions included ways in which this system, both, reduces greenhouse gas emissions and allows landfills to sell bioenergy back to the energy grid.

Technical Abstract: A pilot-scale (1800'kg per batch capacity) autoclave used in this study reduces municipal solid waste to a debris contaminated pulp product that is efficiently separated into its renewable organic content and non-renewable organic content fractions using a rotary trommel screen. The renewable organic content can be recovered at nearly 90% efficiency and the trommel rejects are also much easier to sort for recovery. This study provides the evaluation of autoclave operation, including mass and energy balances for the purpose of integration into organic diversion systems. Several methods of cooking municipal solid waste were explored from indirect oil heating only, a combination of oil and direct steam during the same cooking cycle, and steam only. Gross energy requirements averaged 1290'kJ'kg-1 material in vessel, including the weight of free water and steam added during heating. On average, steam recovery can recoup 43% of the water added and 30% of the energy, supplying on average 40% of steam requirements for the next cook. Steam recycle from one vessel to the next can reduce gross energy requirements to an average of 790'kJ'kg-1.