Power from Pigs?


Being able to produce energy from a waste product while simultaneously cleaning it would appear to be to good to be true. But the project undertaken by Smithfield Foods and Dominion Energy is most definitely real and the benefits are expected to be considerable.

Smithfield Foods is based in North Carolina and runs a number of piggeries. As all piggeries do they produce large amount of effluent that is commonly left in piles to break down or in effluent ponds. But they’ve decided there is a better way and alongside Dominion Energy are embarking on the most ambitious project of its kind, a $250 million investment in biogas capture.

In New Zealand we like to shy away from the fact that farm emissions do contribute significant amounts of methane into the atmosphere which contribute to global warming. But this project provides a prime example of how these emissions can be captured and put to good use. By covering the manure lagoons where effluent is left to digest and naturally break down, the methane that is released from the surface in large amounts can be captured.

Now this not a single benefit situation with the methane being prevented from entering the atmosphere, there is the added benefit of the fact that the methane has a large amount of energy stored in it. Each m³ of methane captured holds around 10 kWh which, at current residential electricity prices, could be as valuable as $2.50/m³.

The Smithfield and Dominion Energy project is on a different scale to what has been tried in New Zealand. The project utilises the 100,000 km of natural gas distribution pipelines that Dominion owns similar to the natural gas distribution system in the North Island. By connecting these farms to the network, the methane can be distributed to residential customers and burnt just as you would the ground extracted methane.

So, to summarise, the project is planning to remove 85,000 metric tons of methane from the atmosphere each year the equivalent of 2,000,000 kg of CO2 (25 Year Horizon) which is total output of carbon produced on a per capita basis by the entirety of Dunedin.

There’s been some interesting steps in this field in New Zealand utilising the number eight wire mentality examples such as this example in Southland. But with the possible inclusion of methane emissions in carbon taxes in the coming years perhaps projects similar to this example will become more commonplace.

It also has the benefit of removing large amounts of the BOD and COD from the wastewater stream which can reduce discharge effects and costs.

All in all it’s a pretty cool innovation and something that could have a real place in the New Zealand farming industry of the Future.

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