Current piggery waste management
Piggery shed effluent/wastewater, which contains urine and dung and may contain wash water, chemicals and rainwater. Urine and dung that dries before being collected is handled as a semi-solid or solid and called manure.Most piggery owners dispose of manure/effluent by:
- letting it compost in the piggery (with straw) or in a pile (on a cement slab)
- putting liquid manure into a concrete storage pit, then into large outside storage containers
- letting it flow into a lagoon to be digested by microorganisms to ‘clean’ it of organic solids (and the produced methane burnt off).
Benefits of using effluent/manure for bioenergyInstead of burning off the methane or using it as compost/fertiliser, piggery owners can choose to capture the methane from lagoons/ponds (and turn that into electricity or heat), or use the waste to produce liquid fuel. If a piggery operator wants to use effluent/manure for bioenergy, they commonly use that energy themselves and do not on-sell it. Using manure/effluent to create bioenergy has many benefits, such as:
- reducing the amount of waste that needs to be disposed of
- recovering energy from waste
- reducing odour problems
- reducing potential for groundwater contamination
- giving a use to waste that previously had little or no market or environmental value
- reducing water use by reusing washing water for the plant/lagoon
- generating income from waste/diversifying income sources
- moderating the impacts of commodity prices
- killing harmful bacteria, flies and weed seeds normally in and around manure
- converting organic nitrogen into a form available to be used by plants.
Calculating potential manure and energyTo work out whether bioenergy from your piggery waste is appropriate for your business, it’s important to know:
- how much waste your piggery produces
- what the nutrient content of the waste is
- how much energy could be produced from the waste.
Evaluating the economicsA 2013 study done for the Pork CRC outlines the economic feasibility of capturing biogas and generating energy [PDF, 393 kB], with short payback times and substantial positive returns within 10 years, at 5 piggeries:
- South Australia, farrow-to-finish, weaners + 500 sows; combined heat and power determined most feasible using a staged approach
- South Australia, grow-out; generator to produce electricity determined most feasible
- Western Australia, sow multiplier unit; CAP and boiler determined most feasible using a staged approach
- Western Australia, sow farrow-to-finish; generator to produce electricity determined most feasible
- New Zealand, sow farrow-to-finish; existing pond covered and biogas equipment installed determined most feasible
- select the right type of equipment
- lay out a plant
- choose the best storage method.
- explores the viability of methane capture and use systems for the Australian intensive livestock industry
- reviews existing manure methane systems from intensive livestock industries operating within Australia and overseas
- presents technologies that are best suited for capturing methane in the Australian context.
Incentives for reducing emissionsUnder the Carbon Farming Initiative, you can earn sellable carbon credits for destroying the methane generated from manure in your piggery by, for example:
- covering effluent lagoons to prevent the release of methane into the atmosphere
- collecting the biogas from the covered lagoons
- combusting the biogas, using it to heat boilers and farrowing sheds and/or generating renewable electricity.
Calculating your emissionsAustralian Pork assessed 2 types of farrow-to-finish piggery in the 2010 report, Environmental Assessment of Two Pork Supply Chains using Life Cycle Assessment (see page 77):
- using tunnel ventilated, flushing sheds in northern Australia
- housing grow-out pigs in deep-litter sheds in southern Australia .
- 5.5 kg with no mitigation of pond methane, or 2.3 kg with pond covering and flaring (northern supply chain)
- 3.1 kg with no mitigation of pond methane, or 2.7 kg with pond covering and flaring (southern supply chain).
Converting piggery waste to bioenergyPiggery effluent/manure can be turned into bioenergy through two processes.
- Biological processes
- uses anaerobic processes or microorganisms
- produces biogas, liquid fuel and nutrient-rich solids
- Thermochemical processes
- uses heat or chemicals
- produces biogas, hydrocarbon fuel (bio-oil) and charcoal.
Anaerobic digestionMany piggery owners already use anaerobic digestion to treat waste, so it is the most commonly used process for producing bioenergy.It uses simple bacteria to break down waste in oxygen-free conditions (anaerobic) to produce biogas and nutrient-rich solids. You can use biogas, solids and cleaner waste water for:
- heating or electricity, by burning biogas in a boiler, heater or engine
- natural gas, by further processing the biogas
- fertiliser, by using the ‘undigested’ solid remains
- irrigation, by using the water separated from the solids.
- a ‘lagoon’ or pond that holds effluent, covered with an airtight cover that collects biogas
- ‘complete mixed’ digestion in heated above- or below-ground tanks full of effluent
- ‘fixed film’ digestion in a tank packed with materials that the microorganisms grow on
- ‘plug-flow’ digestion in heated underground tanks, where effluent is put through semi-regularly.
- collecting the piggery effluent
- removing grit
- thickening the waste
- putting the waste through 2 rounds of anaerobic digestion (and making potting mix and organic fertiliser from the byproducts)
- purifying the biogas to remove sulfide
- generating electricity by combusting methane gas in a generator (called a ‘genset’)
- using the waste heat from the gensets to heat thermal pads in winter and cool pens in summer.
- designing and constructing a biogas plant
- being safe around biogas
- using and storing biogas
- training people
- managing risks
- managing flares, air, noise, odour and effluent
- operating and maintaining the plant.
- Suitable types of anaerobic digesters, yields of biogas, and costs/benefits [PDF 215 KB], compared to conventional alternatives, are detailed in Chapter 8.1 of Dairy Australia report from 2008.
- Instructions about how to use a pond for anaerobic digestion of effluent [PDF 540 KB] are given in a fact sheet from Dairying for Tomorrow program fact sheet.
- Read about supply, infrastructure requirements, costs, incentives and managing risks of anaerobic digestion ponds [PDF 1.4 MB] in a Dairy Australia fact sheet.
MicroorganismsPutting waste in specialised tanks/containers with microorganisms produces hydrogen [PDF 183 KB], which can be burnt for heat/electricity. The microorganisms include:
- algae, using photosynthesis
- bacteria, using fermentation in lit conditions
- bacteria, using fermentation in the dark.
Thermochemical methodsHeat or chemical processes also exist for converting waste to energy: pyrolysis, gasification and direct liquefaction. Two of these may be suitable for your piggery waste:
- Pyrolysis: heating waste to very high temperatures without oxygen to form solid (biochar), liquid (bio-oil) and/or gases (syngas) depending on the speed and temperature of the process. The gases and compounds in the liquids can be used to generate bioenergy.
- Gasification: heating waste to high temperatures with a limited supply of oxygen so it is only partly burnt and produces syngas and a small amount of biochar.
West Street, Toowoomba Qld 4350,
West Street, Toowoomba Qld 4350,
Phone: +61 7 4631 1011
LEVEL 1, 9 GARDNER CLOSE, MILTON, 4064,
LEVEL 1, 9 GARDNER CLOSE, MILTON, 4064,
Phone: Ph: +61 7 3721 7588 | Fax: +61 7 3721 7599 | Mob: +61 405 412 078