Turning food waste into biogas

McCain Foods will boost its conversion of food waste to biogas, saving on energy use and reducing landfill over the next year, says Graham Harvey, the Australia/New Zealand Operations Director.

Harvey said: “McCain Foods has been a pioneer of this process, and we are now looking at replacing 10% of the natural gas use at the plant with biogas.

McCain Foods operates two deep covered lagoons at the Ballarat site: a 6 m deep - 11 ML, and a 10 m deep 28 ML lagoon, undergoing anaerobic treatment of food wastewater.

The anaerobic decomposition of food wastewater produces biogas, which is 65% methane, and when blended with natural gas replaces the use of fossil fuels.

The on-site anaerobic process now produces 6500 m² of biogas daily from wastewater from the plant. After anaerobic fermentation of the wastewater, its strength is reduced by 90% before it’s sent to the municipal plant.

Over 80% of the biogas is used to produce steam to heat water at the plant, which is up from the 50% a year ago.

McCain Foods expects to improve its systems over the next year to use around 95% of the biogas produced.

McCain Foods was one of the first food companies to blend biogas with natural gas in a three-megawatt boiler to produce steam.

Harvey said that increased use of biogas could be achieved with the conversion of around 30% of the 3000 tonnes of food waste, which is currently going directly to landfill.

He said plant engineers were also looking at the potential conversion of some of the potato solid waste now sold for stock feed, which could also produce Biogas.

McCain Foods have been using anaerobic conversion to treat wastewater since the mid-eighties, firstly with the 6 m deep lagoon and then more recently with the larger one.

The company received a $70,000 grant to work with the Victorian Gas and Fuel Corporation in the early 1980s to conduct a feasibility study into the blending of natural gas and biogas in a boiler.

In 1996, McCain Foods invested over $3 million to construct the second covered lagoon to expand the biogas conversion process. And last year, the group further invested $200,000 to increase efficiency of the use of biogas.