Danish firm DONG Energy has begun building one of the world’s first bioresource power plants that will produce electricity from household waste by using enzymes to convert the waste to biogas.
The commercial 5-MW plant under construction in the UK city of Northwich could be commissioned in early 2017. It will use the company’s proprietary REnescience technology, which has been tested at a demonstration plant in Copenhagen since 2009.
The process involves mechanical sorting of residual waste arriving at the plant to remove recyclable and inert materials. Using REnescience technology, enzymes supplied by commercial bioenergy firm Novozymes are then used to remove organic material from the waste in a low-intensity process. “The enzymes are mixed together with warm water and the waste inside a sealed vessel, where they are able to reach and break down all of the organic matter. This means that the organic matter can be efficiently extracted from the other waste so that separate shredding or incinerating at the facility is not required,” said DONG Energy.
The separated organic material is recovered as a thin bioliquid that is then digested by bacteria within a sealed anaerobic digestion vessel to produce biogas. That biogas is captured and used to generate power. “Heat is also recycled within the process, making it almost self-sustaining during operation,” the company said.
The $80 million plant will treat an annual capacity of 120,000 metric tons of waste (which corresponds to waste from almost 110,000 households) supplied by UK waste management company FCC Environment. DONG Energy said a “considerable amount” of recyclable plastics and metals will also be generated. According to FCC Environment group development director Richard Belfield, the technology holds promise for the future of municipal residual waste disposal. “Not only does this technology convert waste into energy without the need for the combustion of the waste, it will for the first time, be able to extract the valuable recyclable materials which so far have been difficult if not out of reach in traditional municipal residual waste treatment processes,” he said.
DONG Energy’s REnescience technology is being explored by a number of countries. Last April, the company entered into a cooperation agreement with Malaysia’s largest waste management firm, Cenviro, to test the technology on its “wetter” waste via a mobile version of the REnescience plant (Figure 2). “The content of waste differs [considerably] from country to country,” DONG Energy noted. The company said it is “planning to send the mobile plant to other Asian countries to test whether there is an export market for it.”
—Sonal Patel, associate editor
Correction (Sept. 1, 2016): $80 million is the estimated cost of DONG Energy’s REnescience plant in northern England, not the value of the contract it signed with Novozymes as had been noted.