Effluent gas flux characterization during pyrolysis of chicken manure

Authors: CLARK, SYDNEY - Brown University; RYALS, REBECCA - University Of Hawaii; MILLER, DAVID - Brown University; Mullen, Charles; PAN, D - Princeton University; ZONDLO, M - Princeton University; Boateng, Akwasi; HASTINGS, MEREDITH - Brown University

Submitted to: ACS Sustainable Chemistry & Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/2017
Publication Date: 7/17/2017
Publication URL: https://handle.nal.usda.gov/10113/5799218
Citation: Clark, S.C., Ryals, R.A., Miller, D., Mullen, C.A., Pan, D., Zondlo, M.A., Boateng, A.A., Hastings, M.G. 2017. Effluent gas flux characterization during pyrolysis of chicken manure. ACS Sustainable Chemistry & Engineering. 5:7568-7575.

Interpretive Summary: Within the Chesapeake Bay Watershed, an estimated 261 million kg of excess manure is applied in the region to agricultural soils every year. This is a source of several environmental problems including nutrient run off into the bay, but also emissions of both carbon and nitrogen gases that are either pollutants or greenhouse gases or both. These emissions include carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), ammonia (NH3), and nitrogen oxide (NOx) gases. One alternative option for utilization of chicken manure is for renewable energy production via pyrolysis. Pyrolysis is the heating of a substance in the absence of air and can produce bio-oil which can be an intermediate for production of bio-fuels and bio-char which can be used a soil amendment with lesser emissions and runoff than the raw manure. However, for the potential environmental benefits of pyrolysis conversion compared with spreading of raw manure to be verified and quantified the emissions of the pyrolysis process must be considered. In this study we pyrolyzed chicken manure and measured the gaseous emissions. The main carbon emissions were CO and CO2 while the 99% of the nitrogen emissions were NH3. The rate of the emissions was also determined. This information was used to compare the emissions of NH3 from conversion of chicken manure via pyrolysis with spreading of the raw manure, and it was estimated that using pyrolysis would emit between 12 and 37% of the ammonia that spreading raw manure does. This information will be useful to those considering utilization of chicken manure in a biorefinery to produce renewable energy carriers and bio-char and also lessen the environmental impact of manure spreading.

Technical Abstract: Pyrolysis is a viable option for the production of renewable energy and agricultural resources from diverted organic waste streams. This high temperature thermochemical process yields material with beneficial reuses, including bio-oil and biochar. Gaseous forms of carbon (C) and nitrogen (N) are also emitted during pyrolysis. The effluent mass emission rates from pyrolysis are not well characterized, thus limiting proper evaluation of the environmental benefits or costs of pyrolysis products. We present the first comprehensive suite of C and N mass emission rate measurements of a biomass pyrolysis process that uses chicken manure as the feedstock to produce biochar and bio-oil. Two chicken manure fast pyrolysis experiments were conducted at controlled temperature ranges of 450 - 485 degrees C and 550 - 585 degrees C. Mass emission rates of nitrous oxide (N2O), nitric oxide (NO), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4) and ammonia (NH3) were measured using trace gas analyzers. Based on the system mass balance, 23-25% of the total mass of the manure feedstock was emitted as gas, while 52-55% and 23% were converted to bio-oil and biochar, respectively. CO2 and NH3 were the dominant gaseous species by mass, accounting for 58 - 65% of total C mass emitted and 99% of total N mass emitted, respectively. Temperature variations within the two set of temperature ranges had a perfunctory effect on bio-oil production and gaseous emissions but the higher temperature range process produced more bio-oil and slightly less emissions. However a larger effect on the relative amounts of CO and CO2 produced were observed between the different temperature regimes. These results have important implications for greenhouse gas and reactive nitrogen life cycle assessments of biochar and bio-oil.