Open Windrow Composting


Highfields' open windrow composting facility at Cowpen Bewley can treat a wide range of waste streams to produce a CLO material suitable for land restoration of our landfill at Cowpen Bewley.


We chose an open windrow composting method. This method involves forming organic waste into rows of long piles called “windrows” and aerating them periodically by mechanically turning the windrows.

Compost Like Output

The CLO from our treatment process is used as part of the restoration requirements of our landfill site at Cowpen Bewley. This material is produced following a strict composting process.


EWC Codes

The use of EWC codes is legally required as part the Duty of Care (DoC) legislation across the UK.

Here is a list of the top 10 wastes that are treated in our Cowpen Bewley Composting Facility.

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The objectives of composting have traditionally been to biologically convert putrescible organics into a stabilised form and to destroy organisms pathogenic to humans. Composting is also capable of destroying plant diseases, weed seeds, insects and insect eggs. Odor potential from composting is greatly reduced because organics that remain after proper composting are relatively stable with low rates of decomposition.

Composting can also effect considerable drying, which has particular value with wet substrates such as municipal and industrial sludges. Decomposition of substrate organics together with drying during composting can reduce the cost of subsequent handling and increase attractiveness of compost for reuse or disposal.

If you have a waste stream, for composting, please reference our Environmental Permit or visit our team page to find a useful contact for some advice.


First of all, we form pre-mixed organic materials into long rows, piled to a height of between four to eight feet, these long piles are called, “windrows”. At their base, they are approximately fourteen to eighteen feet wide. We aerate the windrows by regularly turning and mixing each pile with a specialised machine called a "windrow turner". The size of the pile is critical, it needs to be sufficiently large, so that enough heat is generated to maintain temperatures but then again, not too big as to restrict oxygen flow to the core of the windrow.

Temperatures maintained higher than 55oC for a minimum of 15 days are required to evaporate moisture and effectively kill pathogens. Aeration of the pile is crucial to prevent anaerobic conditions forming thus allowing for efficient decomposition of the organic materials.


Composts which have been produced from mixed waste, which has not been source-segregated are known as compost like output (CLO). CLOs are normally of a poorer quality and varied in their composition. These outputs are ideal for use in land remediation, restoration, and can be used as an alternative for landfill cover.

With this in mind, even though CLO's are not suitable for use as compost in the farming of edible crops, they still have value and shouldn't be ruled out from being utilised in a limited marketplace.

The CLO that Highfield produce at their Cowpen Bewley Composting Facility offers many sustainable benefits and advantages to the environment by reducing the need for virgin soils. Because of its stabilised organic content it can improve the constitution of sub-quality soils.


We are able to treat a wide range of sludges at our open windrow composting facility these include nitrogen rich sludges which are blended with carbo sources and composted to produce a stable Compost Like Output.

Sewage Materials

We are able to treat a wide range of sewage materials in our composting facility, this included sludges and grits from sewerage treatment as well as septic tank wastes. These provide a nitrogen source for the composting process.

Green Wastes and Timber

We can accept a range of green wastes, road sweepings and timber for composting treatment this is utilised as a carbon source in the production of our CLO.


We produce a CLO from our open windrow composting facility, this is used in the ongoing restoration of our Cowpen Bewley Landfill Site which is undergoing capping and restoration.

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