Landfill Pollution to Energy Solution

Pembrokeshire has awoken to the disaster of human and animal sewage damaging our waterways. But what of our other waste streams?

Jamie Ashe reports

We arrived at our second recycling facility to a jollier vibe, more farmer biologist than James Bond. A stormy-down anaerobic digestion (AD) plant near Bridgend is where all our food waste goes and some commercial waste. Lorries dump their load into a concrete pit about 7m X 10m with a second one in case the first needs maintenance. A tanker with liquid waste from a cheese factory arrived while we waited. A hydraulic ram pushed the waste to a conveyor, and up it went and was dropped into a huge blender, which chopped up the little bags of food waste we put in our caddies, and added liquid—water or wey from the tanker of dairy waste.

A centrifuge then spun the wet food waste, flinging it through holes on the sides. The plastic bags we lined our bins with did not pass the holes, they were compressed, removing moisture, and then spat out into a pile. The bags would go off to the Cardiff Energy Waste Place down the road. So in fact, it doesn’t matter if you use biodegradable or plastic bags for putting food waste in, as it all gets burned for energy.

Out of the sides of the centrifuge poured a gloopy chopped-up food soup. We were taken around to see it flowing down the pipe, it was a brown puke colour and you could see lumps in it. A couple of our group members held their noses because of the smell.  I slightly gagged at the ‘puke of wales’ flowing past. The building had overhead air extractors sending smelly air through a container of wood chips seeded with bacteria, which broke down the smells, as a result, there was no smell outside.

The gloupy soup was then pumped into huge tanks, each about the floor area of an Olympic swimming pool and 17m high. Here, it would undergo anaerobic digestion

and gas would collect in large domes above it. The domes would rise and fall depending on how much gas was collected.

There were 3 of these giant silos and gas could be pumped between them to equalize storage or one could be emptied in case of maintenance. Lightning had hit one, producing a large flame, but it could be isolated by closing valves, so no gas from the other tanks caught fire.

After a final extraction chamber, the gas was ‘scrubbed’ by spraying water, which removed sulfur, which could damage the gas engine. Engines in shipping containers burned the gas, powering a shaft to turn a generator. The energy output was 3 mW in total.

The by-product of the process is a liquid fertilizer pumped into 2 lagoons on an adjacent farm. A tenant farmer uses it to fertilize 4500 acres of land owned by the AD plant. He grows a variety of food crops but also a small area of maize to feed the AD plant if there is a shortage in food waste for a few days and maize helps reduce the acidity of the food waste.

The AD reservoirs were essentially large stomachs and needed the right bacteria to digest the food. The manager told us that each huge ‘stomach’ had developed a different taste and did well with different feedstock. One did well when fed bread. These huge round silos with green domes on top suddenly appeared like sentient beings with personal preferences!

The site produces waste heat, enough to heat a housing estate via a district heating system. If it were in Germany or Sweden, this would have happened, but, for some reason, not in Britain. I suggested heated greenhouses growing tomatoes, etc. Another idea was a large domed ‘world’ containing heated swimming pools and tropical plants. I often thought our Bluestone swimming pool, instead of being in the National Park and heated with good land used to grow miscanthus and willow, should have been near Milford Haven power station which is sending all its waste heat into the Estuary.

But at stormy AD plant, as I stood around the pit of food waste bags and breathed in the pungent air, the saying “where there’s muck, there’s money” came to mind. The constant output of 3000 kW would be worth at least 13.6p per kWh, which would be an income of £10,000 per day or £3.6 million per year. On top of this would be the gate fees for collecting the waste, which would be even more.

If Pembrokeshire residents could compost their food waste, it would save the council a lot of money in staff time, fuel costs, and gate fees to get rid of it. A third of our council tax bill goes on recycling and the environment. The more we compost at home, the better, but food waste could create gas close to home if it were easier for farmers to receive domestic waste. The cost and barriers to a license make this impossible, so instead, it is driven to Bridgend. Or it could simply be composted locally with heat and soil fertility for our use.

Not long ago, food waste was just thrown in with all the rubbish, which went to landfills, causing rats and polluting leachate.  The stormy down AD plant technology came from Germany; they even have a guy called Wolfgang who comes over to tell them how to be more efficient. It was in 2019 that Cris Tomos, as cabinet member brought in our household separation system, placing Pembrokeshire as the lead recycling county in Wales, and Wales became second best in Europe.

There is great scope for the export of AD, waste-to-energy technology and expertise, and general waste management systems around the world. Just as the technology matures and becomes available, we are seeing massive species losses and climate change catastrophes gathering pace.  It feels like we are making a last-minute effort to save the planet from destruction.

I feel privileged to live through these times and see recycling take off in Wales. As the place where the industrial revolution started, it feels right that it is the place that leads the way in tackling the huge global environmental problems that industrialisation has caused.