Spotlight on Welsh Water Organic Energy

As it’s zero waste week, I thought I’d share some information on Welsh Water Organic Energy and how they are helping combat climate change.

Tell us about the Organic Energy project at Welsh Water?

So Welsh Water Organic Energy is a partnership with Cardiff and the Vale of Glamorgan Councils. We operate two sites in Cardiff. The first is the food waste site which is next to Welsh Water’s Cardiff East Wastewater Treatment Works on Rover Way in Tremorfa. The other is our garden waste site on Lamby Way. We use food waste to produce energy and quality grade fertiliser, and garden waste to produce compost.

We treat the food waste through a process called anaerobic digestion. Anaerobic digestion is a process which occurs naturally, in the absence of oxygen, as bacteria break down organic materials and produce biogas. When the food waste arrives on site it gets placed into the fermentation tanks to begin anaerobic digestion. Here the food waste is broken down by enzymes at a temperature of 38 degrees, and it is at this point the food starts to create biogas, a mixture of gases primarily consisting of methane. This process takes around 28-32 days to break down. Once the process is complete, the final product is pasteurised at 71 degrees for an hour to kill off any germs such as E-Coli or Salmonella. The two by-products produced are biogas and digestate.

We process garden waste by composting. Composting is a natural biological process in which organisms break down organic matter in the presence of oxygen. At Lamby Way the garden waste is processed through windrow composting, which is the production of compost by piling organic matter in long rows. The waste is shredded, mixed and put into windrows which are regularly turned to regulate heat and moisture and improve oxygen content. On average this take 8-10 weeks, before it produces compost.

What are the benefits of these by-products to the environment?

In relation to food waste, if this had made its way to landfill it would have produced a potent greenhouse gas called methane which would have been able to escape into the atmosphere, contributing to climate change. Methane is a potent greenhouse gas due to its high global warming potential, 28-36 times. Global warming potential, GWP, is a measure of how much energy the emissions of a gas will absorb, the larger the GWP the more the gas will warm the Earth compared to CO2 over the same time period (the time period usually used is 100 years).

By treating it through anaerobic digestion, we can capture the methane, and then use it to fuel an engine which creates an energy source. We use the heat within our treatment process, and the electricity generated allows the site to be self sufficient with the remainder being used to power our neighbouring wastewater treatment works.

The other product from the process is digestate, which can be used by farmers for agricultural purposes or by horticulture establishments, meaning they are replacing the use of fossil-fuel intensive fertilisers.

By composting our green waste, the methane emissions are significantly reduced. The compost produced can then be used for landscaping and building projects, production of topsoil or as a soil conditioner within the agricultural sector. Both process help promote a circular economy.

Why is reducing waste so important in the global fight against climate change?

Recycling or repurposing helps to tackle climate change by decreasing the amount of fossil fuel intensive processes for example used to extract raw materials or manufacture raw materials.

What’s your favourite environmental hack?

Aside from repurposing items, my favourite is replacing my currently unsustainable/less sustainable items with a sustainable one when I’m done with it. A simple swap we can all do is swapping to shampoo bars/refill shampoo and conditioner.