Food waste to energy

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Deerdykes plant in Lancashire, UK

The recycling of waste is always a hot topic in New Zealand. During the process of manufacturing a lot of waste is generated. How this waste is dealt with differs from factory to factory. In New Zealand the majority of green and putrescent waste is sent out to pig farmers to be used as feed or is sent to landfill.

As part of the government’s drive to meet its environmental targets, landfill taxes are rising steeply, and producers and processors which generate waste are searching for the most efficient way to minimise costs.

Unfortunately for the pigs, waste containing large amounts of organic matter is a valuable commodity. It can be recycled into gas, electricity and a high quality fertiliser.

This is done by installing an anaerobic digestion (AD) tank which turns food waste into energy.

An example of a successfully operating bio digester is the Anaerobic Food Digester that Scottish Water Horizons has installed in Lanarkshire in 2011. It is one of the most advanced plants of its type in the UK, installed to take advantage of the growing food waste problem in the UK and also to claim green energy tariffs for renewable power generation.

The site utilises anaerobic digestion technology to turn 30,000 tonnes per annum of solid and liquid food waste into energy at a rate of 1MWe (enough electricity to power up to 2,000 homes).

The plant treats food waste (from local authorities, supermarkets and manufacturers) for 15-20 days and converts it to biogas. The plant uses a sophisticated de-packaging system that removes all the packaging from incoming food waste and produces a clean, organic slurry for the digestion process. By adopting this type of process configuration, it means the plant can accept a large variety of food waste types from all across the region.

The unit harnesses biogas produced by the break-down of organic materials. The biogas is then used in a combined heat and power engine to produce electricity and heat. This means that not only is more waste efficiently recycled, away from landfill, but that the Deerdykes plant is self-sufficient in energy and more. Any surplus is used to power the neighbouring industrial estate or sold back to the national grid. The process also produces nutrient rich digestate, which can be used as a fertiliser to improve the nutritional content of Scotland’s soil resources.

It has been recently found that Scottish households throw away a billion pounds worth of food every year, amounting to 570,000 tonnes of discarded food and drink.

Chris Banks, commercial director at Scottish Water Horizons, said: “This new plant shows we’re leading the way, not just on renewable energy, but in helping Scotland towards its ambition of zero waste. As environmental and recycling targets become even tighter we expect others will follow the lead of Scottish Water Horizons.”

Duncan McLaren, chief executive of Friends of the Earth Scotland, said: “This is an example of a big company taking sound initiative to help address the twin problems of climate change and excessive organic waste being sent to landfill.”

The anaerobic digester unit was supplied and built by Monsal, who are the market leaders in the provision of digester technology.

The bio-waste plants are offered as complete turnkey installations with a primary focus on high levels of organics separation and high levels of performance and energy efficiency.

Factories in New Zealand could look ahead and utilise this innovative technique.

JIPL are the New Zealand agent for Monsal’s advanced technology, which is specifically designed to recycle biowaste into valuable products at a low operating cost.

For more information:

JIPL Visit: www.jipl.co.nz

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