Visit to industrial and domestic bio-digesters

March 15th, 2012

Fifteen people, mostly local residents of Motueka and Nelson, on Sunday visited the York Valley landfill in Bishopdale, Nelson to observe and learn about industrial and domestic style bio-digesters.

The visit was organised by the Motueka-based group known as The Renewables, a group working to highlight the importance of renewable energy initiatives rather than new fossil fuel extraction.

Methane biogas from the York Valley landfill is providing the Nelson hospital with a huge reduction in use of coal in it's boilers. The landfill waste, which comes from domestic and industrial sources, produces methane gas which is captured and piped 2km to the hospital. The 2-megawatt boiler there produces over 60% of the hospital's thermal energy demand for heating, hot water and steam.

The biodigester system which captures this gas is a partnership between the Nelson City Council, Nelson Hospital and Energy For Industry who installed and continues to run the system. Energy For Industry is a subsidiary of state owned enterprise Meridian Energy.

The 15 people braved moist weather conditions on Sunday to look at the landfill site and methane production at the landfill. Renewables group member Katerina Seligman explains, "The use of natural gas at the Nelson hospital lowers the need for the extraction of coal.

"We don't need foreign companies digging up the wilderness on the Denniston Plateau, or mining for lignite in Southland. We could just use the energy that's being generated in our landfills and going to waste. Imagine what it could do for the climate if we saw more hospitals, schools and our public transport systems converting to biogas as a form of energy."

After the tour of the site, the group went on to the Nelson Environment Centre to cook lunch on the domestic-size biodigester there. Bill Rucks, Russell McGuigan and Al Wilke are taking the biodigestion method to homeowners, through a local company called Waste Action Limited.

Russell says, "Energy can be tapped from what most people are calling waste." By installing a simple low cost structure and feeding it household waste, people can fuel their own homes with natural gas produced on site.

Helen Tulett says, "I'm really keen to get a biodigester installed. It's great to think I can recycle all my green waste and get 3 hours of gas for cooking to use a day. And the only by-product is compost for my garden. I'm worried about the government selling off our energy companies. I'll have better control of my energy costs with my own biodigester" she said.

Comment by John Hill:
[Posted 21 April 2011]

Your article relating to the landfill gas capture system at York Valley landfill is sadly not all good news. The reason that landfills produce methane (a potent greenhouse gas) is that the organic component of waste namely kitchen waste and garden waste anaerobically digests in the absence of oxygen in the landfill to produce methane.

It is a simple process to separate kitchen waste and garden waste and divert this organic waste from landfill and put it to beneficial use such as commercial composting or preferably anaerobic digestion. Nelson City Council can inplement this process immediately if they had the will. Divering organic waste from landfill prevents the production of landfill gas and removes the landfill operator's obligation under the emissions trading scheme.

Landfill gas capture aims to collect methane which has been produced in landfill but it is only 50% efficient. 50% of the landfill methane remains available to enter the upper atmosphere.

The problem this creates is that in the case of York Valley landfill, a 15 year contract was entered into between Nelson City Council, Energy for Industry and Nelson Marlborough District Health Board to supply landfill gas derived energy to the hospital. Clearly this contract requires the continual supply of organic waste to York Valley which is in contradiction to the Ministry for the Environment directive of zero landfill gas emissions by 2010.

Rather than being green this project is interfering with the process of reducing landfill gas emissions and is not green.

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