Roof Lift Improves Composting

In order to increase the efficiency of In-Vessel Composting (IVC) plant Power Jacks were asked to provide a linear motion system for The Composting Company’s unique composting process.

An In-Vessel Composting (IVC) Plant processes biodegradable household and commercial material to produce a quality compost product for use in agriculture, landscaping, top dressing and by the public. It diverts waste from landfill and helps reduce the release of methane - a powerful greenhouse gas impacting climate change. The IVC is fully compliant with the Animal By-Products Regulations (ABPR) for the processing of food inclusive material.

The Composting Company’s IVC vessels are unique in that they have a lifting roof with a patent pending on the system. The reason for this is to allow access for the loading shovels when opened, and when closed it provides a small void space above the material to allow for better control over the process. The roof is positioned by a linear motion system designed and manufactured by Power Jacks.

Providing the linear motion for each roof are two individually motorised screw jack systems, synchronised electronically to operate in unison. The jacking system raise and lower the roof via a simple push button operation and can lift the roof over its complete two metre stroke in less than 1 minute. The screw jacks used in the systems are Power Jacks classic E-Series single face screw jack, that is popular choice for customers around the world designing jacking systems due to its performance, robustness and reliability. For this application 100kN rated capacity models were used to provide adequate load rating and structural rigidity. Originally when development started in 2007 the application used UE1811 upright rotating screw jacks, however this has now changed to ME1810 upright translating screw jacks as the IVC design developed. This has resulted in an improved roof structure and mechanism that also benefits from the integrated dual lubrication mechanism inside the E-Series translating screw jack.

The screw jacks are aligned along the side wall of each vessel, one at each corner and one in the centre. The screw jacks are situated inside the wall and connected to the roof. Each wall has a motor that drives the screw jacks on that particular wall with the two motors synchronised for each side of the vessel. When lowered the screw jacks are protected inside the wall and they operate in a non-hazardous environment as they are outside the vessel where corrosive atmosphere exists.

The composting process starts when material is delivered to site and tipped inside a reception building where the pre-processing work is carried out. The material is then shredded and mixed before being removed to the first of two barriers of composting vessels. Moisture is also checked to ensure that it has around 60% moisture which is important for the composting bacterial activity.

The roof on a vessel in Barrier-1 is lifted to its full height by the screw jack system in less than one minute to allow access to a loading shovel to load in the shredded, mixed material. When loaded, temperature monitoring probes are placed into the material and the roof is lowered. The aeration system is activated and this circulates air through the material in the vessel to maintain oxygen levels.

Composting is a natural biological process that requires aerobic conditions and moisture for the composting bacteria to work well. The Composting Company’s aeration system monitors the level of oxygen in each individual vessel as the oxygen demand will vary from vessel to vessel depending on the mix of material and the stage of the process. When oxygen reaches a minimum parameter the aeration system automatically draws in fresh air to replenish oxygen and exhausts stale air to a biofilter. A proprietary SCADA system monitors both oxygen and temperature and allows for remote alteration of settings if required.

Temperature also has to be monitored to comply with the Animal By-Products Regulations (ABPR) for the processing of food waste which requires a temperature of 600C to be achieved for at least 48 hours in order to kill off pathogens. In practice the material stays in the vessel for 7 to 11 days as the controlled environment speeds up the composting process.

After 7 to 11 days the Barrier-1 vessel is unloaded, from the opposite end to which it was loaded, into Barrier-2 and the process is repeated in compliance with ABPR. After 7 to 11 days in Barrier-2 the material is sanitised and is removed to a maturation pad where it is formed into windrows (long piles of compost) and monitored for temperature and oxygen for 4 weeks or more depending on the final application.

When it has matured sufficiently for the application it is screened to a suitable size for the end product and sold to agriculture, landscape gardeners, garden centres or the public.

Each building that houses the vessels requires 2 jacking systems (one per side), each with 3 screw jacks and one motor. To date Power Jacks has provided screw jack systems for 20 IVC’s.

There are currently 4 IVC’s at Cumberlow Compost Services and 16 IVC’s at The West London Composting Company (WLC) and have been in operation since March 2008. The vessels supplied to the WLC site by The Composting Company makes it the largest IVC in Europe with an annual capacity of 100,000 Tonnes.

The Composting Company are currently expanding the number of vessels by 4 at the Cumberlow site and also have other sites asking for their system. As their supplier Power Jacks are providing on-going support and product development for their business and product development.

Roger Hughes, Commercial Director of The Composting Company said, “Power Jacks have provided us with an excellent service throughout the construction of both sites and subsequently whilst dealing with teething problems. The jacks have proven reliable in use, work well and do everything we require of them”.