Power from pig poo

Blantyre farms, owned by Michael & Edwina Beveridge is a pig farm outside of Young, NSW.  The Beveridges have a 2,000-sow piggery, which means that at any point there are about 20,000 pigs on hand. There are two separate piggery sites, a breeder and a grower site. Blantyre has recently installed a methane digestion system at both piggery sites. Blantyre farms was the first in the Australian pig industry to complete a commercial digestion system.

In piggeries, methane is released into the atmospheres from the anaerobic decomposition of pig manure in settling ponds. A methane digestion system captures this gas under a pond cover and burns the methane. When burned, the methane gas is converted to carbon dioxide. Methane has a Global Warming Potential of 21 versus carbon dioxide at 1, meaning that methane is 21 times worse for the atmospher than carbon dioxide.

To set up the anaerobic digester, a new dam was constructed at each of the piggery sites. Each dam holds 50 days worth of effluent. The dam at the grower site holds 15ML, is over 100m in length, 40m wide & 5m deep. The breeder site dam is about a third the size. Each dam has been covered with 2mm LDPE (Low density poly ethylene - a type of plastic) covers. A trench was used to anchor the cover, which was then backfilled. Large PVC pipe capped at the ends & filled with water also help anchor the cover.

 
 

There is a flare on each pond, this is back-up for the generators and will burn the methane, if the generators stop. The gas runs from the pond through a scrubber, which cleans the gas of impurities & then a chiller which removes condensation, it is then piped to the generator.

Quantum Power, a Brisbane based company has supplied Blantyre with the machinery & generators. They are containerized, to reduce noise and allow easy transportation. There are two units at the grower site and one at the breeder site. In summer all three operate, in winter there is only enough gas to run one at each site. This also provides a spare generator, which we can move from site to site as required. The methane gas is a fuel source for a converted diesel engine, which is coupled to a generator. Blantyre has 3 x 80KW generators.

Both separate digestion systems are connected with a pipe that runs for 3.8km and goes under a main road. This allows flexibility and will keep the gas up to the breeder site which uses the most power, but makes less gas. A heat exchanger on the generators exhaust is used to heat water. This water is reticulated through weaner rooms and the farrowing house to provide heat to piglets. In the past this heating had been generated using power & LPG, and the cost saving in utilizing the free heat is significant.

There is a computer controlling the generators which can be accessed remotely. It has an auto alarm which sends text messages when there are problems with the generator.

Blantyre expects the project will have between a two and three year pay back period. The greatest saving have been in producing power for the farm's own use, as electricity charges are about 20c/kW. There is a smaller benefit in selling power to the grid, where Blantyre receives about 3.5c/kW.

As part of the project, the industry body Australian Pork Limited has been proactive with the Carbon Farming Initiative and have registered a methodology “for the destruction of methane generated from manure in piggeries”. This methodology has been approved.

 

 

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