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Anaerobic Digestion

Shanks Orgaworld business gives the group unique access to anaerobic digestion or AD and composting expertise. AD is the conversion of organic waste, such as waste food, into biogas and digestate, a technology used by Orgaworld for over 10 years.

But how does yesterdays spaghetti become tomorrows renewable energy? Firstly, all packaging is removed and sent for use in energy generation in place of fossil fuels. This ability to depackage food waste creates a competitive advantage, as it makes life easier for customers, like retailers and local authorities. The organic material is then blended into a liquid and transferred to storage tanks. These liquids are in effect the raw ingredients for the AD recipe.

A mix of the liquid is then sent to the digester, which is an oxygen-free environment, hence the term anaerobic. Shanks experience means they’re able to optimize the blend, maximizing the amount of biogas produced. The liquid in the digester is heated 30 to 35 degrees and mixed with paddles to avoid separation.

During its 30 or so days in the digester, microbes digest the organic fraction within the liquid and release methane rich biogas. This gas, and the processed liquid called digestate, are then extracted and sent for further treatment.

The biogas gets used in a variety of different ways. It can be operated to vehicle fuel or injected directly into the gas grid, but typically Shanks combusts the biogas to generate renewable energy which is sold to the national grid. This energy attracts renewable obligation certificates, known as ROCs.

The digestate is then treated to separate the solids from the liquid. The liquid is cleaned and discharged back into the sewer, and the solid is recycled back to agricultural land as fertilizer. This reduces the need for expensive inorganic nitrogen and replaces phosphorus whichs comes from a nonrenewable source, so nothing goes to waste.

Legislative and fiscal drivers mean that AD is an increasingly attractive and sustainable solution for private companies or local authorities wishing to meet their environmental commitment whilst increasing recycling and reducing waste in landfill. This makes AD one of the fastest growing segments in the waste management industry, and Shanks experience means that no one is better placed to exploit it.