Biffa Compost Works

Biffa is one of the UK’s largest waste processing companies and specialises in handling and recycling all types of waste and recyclable materials. One of Biffa’s windrow compost facilities is located near Derby. At the facility, an area of concrete hard standing has been established to lay out green waste collected from council and major road work contractors. The purpose of the facility is to compost green waste and produce re-saleable compost for commercial landscapers and other horticultural markets. The process adopted allows for green waste to be transported to the site, shredded and then laid into rows of 150 metres long, 4 metres wide and 4 metres high. The layout allows for vehicle access between the rows and the rows are typically turned every 7-10 days. No additional additives or moisture was introduced before the trial. The average time for composting was 18 weeks.

Background

The facility was stretched to capacity and costings had been assessed to extend the footprint allowing for double the current capacity. Due to the large cost of some of the modern composting systems and the extensive payback period, Biffa decided to evaluate the effectiveness of an Advetec product on production and profitability.

Objectives

The aim of the trial was to improve the following areas related to composting:

• Decrease composting time to PAS 100 standard.
• Ensure no PH deviation of finished product.
• Ensure product CO2 discharge was equal to or better than existing.
• Prevent excessive leachate.

Implementation

A site wide survey was conducted prior to the Advetec dispensing units arrival. During the evaluation period samples were collected and analysis was recorded independently by Biffa. The Advetec 2020 product was dispensed, once weekly for seven weeks, as a fine mist spray from a dispensing unit towed behind a four wheel drive vehicle. The final compost samples were taken from the treated windrow, an adjacent windrow, which had not been treated, and a windrow that had been composting for 18 weeks

Analysis

During the evaluation period the temperature and organic composition where monitored by Biffa staff.

Results

In direct comparison with windrows laid at the same time from the same source material.

• The windrow treated with Advetec 2020 product degraded, in compliance with composting standards, within 9 weeks. The control windrow took another 13 weeks to achieve the same quality.
• In comparisons to the windrow that had been degrading for 18 weeks, the trail windrow material was of a much higher standard. The statistics showed a marked improvement in quality.
• In addition, since the facility was limited by physical size it could now receive a higher volume of green waste to process, this would result in an additional net annual revenue of £86.675.
• During the trial it was noticeable that the leachate, from the rows, appeared clearer and no noticeable odour was detected around the treated windrow.