Solution Strengths, Weaknesses and Critical Indicators
- May produce a soil amendment in the form of biochar or ash
- Biochar does not yet have an established, stable commercial market
- There is significant variation in energy use and recovery depending on feedstock
- There is significant variation of operational intensity by site and by technology, many technologies require pairing with other technologies to offer a comprehensive manure management solution
- There is significant variation of cost depending on site and by technology
- Proven technology for phosphorous recovery, storage reduction, GHG reduction, odor control and pathogen reduction
- This technology loses nitrogen to the atmosphere
- The primary application is thermal treatment of previously separated manure solids to produce higher-value biochar.
- Pyrolysis is designed to process manure solids and sand separated bedded pack.
Economic/Return on Investment Considerations
- The capital cost of pyrolysis systems is relatively high.
- The operating costs of these systems can be low as they can provide their own energy and require no additives if the feedstock is dry enough and has a high enough energy content.
- Depending on the system, pyrolysis can produce a dried bedding material and biochar or bio-oil which are salable products with a limited market at this time.
- The economic viability of pyrolysis of dairy manure needs to be worked out. The results of the residual products testing that is going on across the country will ultimately determine the viability of pyrolysis projects for manure.
- Commercial pyrolysis systems to process cow manure are not currently available.
- Presently, there is limited research being done with pyrolysis that utilizes dairy manure as feedstock and little commercial application due to the high cost of the technology and low value and/or market risk for the products.
- Pyrolysis systems are not commercially available to process dairy manure.
- A limited number of prototype pyrolysis systems are processing poultry and swine manure and one dairy prototype system is processing cow manure to produce biochar and bio-oils.
- Pyrolysis is potentially applicable as a treatment mechanism for dry lot dairy manure or separated manure solids since this process favors drier solids.
- Dairy manure pyrolysis produces char with high amounts of noncombustible material (~50%), which favors the biochar as a soil amendment or remediating-agent rather than as renewable energy.
- Because of the significant volume and mass reductions that occur with the manure during pyrolysis, there is potential savings from storage and transportation.
- Phosphorus and other nutrients are captured in the char and available to be used as fertilizer for crop production.
- Pyrolysis keeps manure solids from being put into on-farm liquid storage. In turn, this prevents the production of greenhouse gases (GHG) and odors. Under the high temperature treatment, pathogens are destroyed.
- The Pyrolysis process is exothermic and therefore produces more energy that it consumes providing a favorable energy balance and significant renewable thermal heat production if the solids in the feedstock is high enough.
- Pyrolysis takes only hours to process manure when compared to other technologies resulting a smaller plant size.
- With emission controls, pyrolysis significantly reduces odors as compared to typical liquid lagoon storage.
- Greenhouse gas (GHG) mitigation is also potentially high as compared to an anaerobic lagoon storage baseline but requires additional research.
How it works?
- Pyrolysis is a process by which biomass solids (including dairy manure solids and bedding) are placed in a sealed chamber in the absence of air and heated to 400 – 1500 F. Because no oxygen is present, the solids do not combust. Instead chemical compounds in the manure decompose into combustible gases and charcoal.
- Most of these combustible gases can be condensed into a liquid fuel, called bio-oil, though there are some permanent gases.
- Thus, pyrolysis of manure produces three products: solid biochar; liquid bio-oil and a gas (syngas).
- The pyrolysis process can be self-sustained, as combustion of the syngas and a portion of bio-oil or biochar can provide all or some of the energy to drive the reaction.
- The bio-oil and solids can be further refined into energy dense liquid fuels and commercial biochar.
Pretreatment and/or Post-treatment Required
- Solid separation and/or drying is required for wet feedstocks.
- If sand is used as bedding, separation is required.
- Additional technology is required to refine bio-oil and solids into energy dense liquid fuels and commercial biochar.
- Nitrogen recovery is limited with significant amounts lost to the air resulting in air quality concerns and nitrogen losses to the farm.
- Pyrolysis capital and O&M costs are not verified, due to the limited number of operating systems in the U.S.
- Does not work well with high moisture content manure or sand bedding.
- Pyrolysis requires dedicated, skilled labor to operate and maintain the plant.
- Pyrolysis economics are a challenge.
- Markets for biochar and bio-oil products need to be developed to generate enough return on investment.
- More research is needed to determine the potential of biochar with respect to carbon sequestration in soil, crop yields and GHG mitigations.
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