Producing biomass: Biomass types: Animal waste: Piggery waste
Effluent or manure from pigs in piggeries can be converted into biogas (a renewable energy source consisting mostly of methane and carbon dioxide), liquid fuel and/or nutrient-rich solids. Biogas can be burnt to generate electricity and heat, upgraded into a transport fuel (biomethane) and can yield other useful products.

Using simple bacteria to break down waste in oxygen-free (anaerobic) conditions is a process called anaerobic digestion. Anaerobic digestion in lagoons or ponds is the most common method used to process piggery waste to create biogas.

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
or
  • letting it flow into a lagoon to be digested by microorganisms to ‘clean’ it of organic solids (and the produced methane burnt off).
From there, they would spread solid or spray liquid waste onto land as fertiliser, or use the relatively clean effluent from lagoons as irrigation water.

What Australia does with its animal waste is described in the 2008 report: Animal waste management country specific profile: Australia [PDF 60 KB, page 4].

Benefits of using effluent/manure for bioenergy

Instead 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.
Some of these benefits are described in the paper Livestock waste-to-bioenergy generation opportunities [PDF 322 KB, page 7941–2].

Calculating potential manure and energy

To 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.
The typical nutrient composition of piggery effluent [PDF 136 KB] is explained in a fact sheet from Australian Pork Limited.

The waste from 20 000 pigs generates roughly the same as the sewage output of a town with a population of about 80 000 people, as measured at the Berrybank Farm Energy Recovery project (Windermere, Victoria).

The amount of effluent from 10 Australian piggeries—and each farm’s physical conditions, its manure management objectives, manure issues, action plan and implementation—are described in case studies by Australian Pork Limited (published 2011).

You can determine the energy potential for your piggery using these steps from the Pork CRC.

To predict how much manure will be produced from an intensive piggery [Excel spreadsheet, 406 KB] you can use PigBal, a nutrient-balance model that you put data into. This version was developed by the Queensland Department of Employment, Economic Development and Innovation in 2012.

Effluent from pig farms may offer immediate potential to harvest methane to produce biogas for electricity [PDF 60 KB, page 5–6], according to a report from 2008 about animal waste management in Australia. There are over 120,000 rural enterprises in Australia with production systems that provide greenhouse gas sources, such as manure.

Evaluating the economics

A 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
The study is summarised in a presentation by Dr Stephan Tait (UQ) [PDF, 7.8 MB].

If you are considering installing lagoons to capture and use the methane generated, refer to the detailed economic considerations/risks and recommendations outlined in Australian Pork Limited’s draft Code of practice for on-farm biogas production and use (piggeries) [PDF, 1.7 MB].

It describes, for example, how to:
  • select the right type of equipment
  • lay out a plant
  • choose the best storage method.
An assessment of methane capture and use from the intensive livestock industry [PDF 1.9 MB] published by RIRDC:
  • 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.
Some projects will only be viable if they also sell the dewatered, digested solids produced as a by-product.

Large, intensive livestock operations may be able to partner with nearby coal-fired power stations or cement works for co-combustion (where the waste would be burned with coal); however this usually isn’t feasible for effluent, which is heavy and expensive to transport.

Although for dairy waste, the typical costs and viability of using covered anaerobic ponds for waste [PDF 1.6 MB] from Australian and US experiences are described in this resource by Dairy Australia.

Using animal waste for biogas is the subject of 14 international case studies described in: The generation of biogas on-farm using animal and dairy waste [PDF 752 KB]. Cost-benefit analyses and technical specifications are covered.

Using methane in intensive livestock industries [PDF 681 KB] outlines many different effluent-treatment options, including costs (see pages 22–29). The report was published by RIRDC in 2008.

Incentives for reducing emissions

Under 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.

Until 1 July 2015, applications for new project registrations can be lodged under the eligibility rules and methods which are currently in place under the Carbon Farming Initiative.

From 1 July 2015, new applications will be assessed under the Emissions Reduction Fund eligibility rules and must apply the most up-to-date version of the relevant method.

Calculating your emissions

Australian 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 .
Producing 1 kilogram of pork produced gases with the global warming potential (in units equivalent to the effect of 1 kilogram of carbon dioxide) of:
  • 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).
To calculate the greenhouse gas emissions from your piggery and the potential carbon farming credits you could earn, you can use the Australian Pork’s PigGas estimator [Excel file, 1 MB]. It follows the calculations used in the estimation of Australia’s Greenhouse Gas Accounts, but allows you to fine-tune piggery production and manure management systems.

You can also download the PigGas user guide [PDF, 1.8 MB], and 6 PigGas case studies [PDF, 386 kB].

Converting piggery waste to bioenergy

Piggery 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.
These processes are described in more detail on a Victorian Department of Primary Industries webpage, and in much more detail in a paper about bioenergy opportunities from livestock waste [PDF 322 KB].

Anaerobic digestion

Many 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.
Anaerobic digestion is possible using:
  • 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.
Effluent quality and volume, temperature, pH, and time all affect how much biogas is produced by anaerobic digestion, and can be carefully controlled to increase production.

The experience of the Berrybank piggery using effluent to generate heat and electricity through an anaerobic digestion process has involved the following steps:
  • 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.
Australian Pork Limited’s draft Code of practice for on-farm biogas production and use [PDF, 1.7 MB] focuses on on-farm, covered anaerobic digestion in Australia, based on international best practice, and is very detailed about logistics of setting up and running a plant.

The report offers guidelines for:
  • 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.
Although these resources are for dairy operations, they contain useful information for piggery owners considering anaerobic digestion:

Microorganisms

Putting 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 methods

Heat 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.

Contacts

Quantum Power

Quantum Power

LEVEL 1, 9 GARDNER CLOSE, MILTON, 4064,
Phone: Ph: +61 7 3721 7588 | Fax: +61 7 3721 7599 | Mob: +61 405 412 078

kunal.kumar@geodynamics.com.au
ADI Systems Ltd

ADI Systems

ADI Systems (Asia Pacific), 50 Yeo Street, Neutral Bay, NSW 2089
Phone: 1.800.751.806 (toll free)

asiapacific@adi.ca