19 July 2002

Steel tube turns waste into profits

Take a large diameter, long

steel tube and pour in all

manner of waste products.

Four days later out comes

valuable fertiliser. Not, it

seems, a latter day

alchemists dream, but a

process which is now in its

final stage of development.

Andy Collings reports

YOU can import the food but you cant export the waste, says Nick Helme, who heads up the newly formed Leominster-based Bioganix company.

A subsidiary of the 7Y farmers co-op group, Bioganix claims to be the first firm to set up and operate an in-vessel composting system capable of processing materials such as feathers, Cat 3 slaughter biproducts and catering waste.

Mr Helme says EU law to be implemented early next year will allow the composting of the latter two products – Cat 3 slaughter waste comprising blood and offal products, but not the potentially dangerous BSE-carrying spinal cord or brain components.

"This development will allow products, which are disposed of less acceptably in landfill sites, to be processed to set standards and recycled as fertiliser," says Mr Helme.

Based near the giant Sun Valley Foods company, which rears many thousands of chickens during the course of a year, the main product being processed at the Bioganix plant is feathers.

Delivered in 20t loads (it takes 95,000 birds to produce this quantity) the feathers are mixed with paper waste, poultry droppings and wood chip in a Seko mixer wagon – the feathers taking a 70% share. This material is then conveyed into the composter unit at about 20t a day.

The composter comprises a steel tube 3.6m (12ft) in diameter and about 15m long. A layer of foam insulation helps to ensure the essential 70C temperature is achieved and maintained during the composting cycle.

Once loaded, the tube and the material within it, is slowly rotated at four revolutions an hour. Power is provided by a 10hp electric motor driving a hydraulic pump which then powers the hydraulic motor.

It takes four days before the composting action is complete, with 20t being taken off the unit each day as 20t of raw material is fed into the other end.

Composted material is then stored for a further 10 days during which time it is turned three times to allow cooling and an element of drying to occur. The result is a fine, powdery substance, each tonne being able to supply 50kg of N, 7.5kg of P and 10kg of K.

Mr Helme uses the facilities of the 7Y group to spread this as a bulk product on land, but the future could see it pelleted and sold through more domestic channels.

With a 20t a day capacity, the Bioganix composters £500,000 investment is still considered to be a pilot operation.

"We have spent a significant amount of time learning how the operation should be performed," says Mr Helme. "One of the secrets is to achieve the right mix of waste products at the right moisture content – crucial if the process is to be a success – and there are other techniques which, frankly, I am not prepared to disclose at this time."

With the finer points of the operation now learnt, there are plans to invest £2m in the construction of a 1000t a week composting plant on a new site – one with a 6m (20ft) diameter tube and twice the length.

Such investment clearly calls for a satisfactory financial return. Mr Helme says the main revenue comes from gate charges – the charge to companies for delivering their waste products for processing.

"We match the charges made by landfill businesses and can offer companies a fixed rate for a number of years, unlike landfill prices which tend to increase each year with tax increases."

Mr Helme feels enthusiastic for the future of the Bioganix enterprise, but there is one aspect of the operation which could potentially be a severe problem.

Smell factor

It is the smell factor. As most will know, most aspects of the poultry business produces more than its share of strong odours. The processing of feathers is probably top of the tree in the smell league.

Mr Helme has made a concerted effort to confine and reduce the amount of odours released by the plant. Among other measures, two air "scrubber" units have been installed.

Seen again as a pilot scheme, which will be adapted for the larger unit, the primary scrubber unit comprises a tank of water with a small amount of sulphuric acid mixed in it to achieve pH4, and a wide tube which extends vertically from it for about 4m. The side of the tube is lined with a plastic comb-type material.

In operation, air passed up the tube meets acidic water coming down – the combs providing a large surface area for the air to be washed of its alkali component – the ammonia. In due course the water becomes concentrated and ends up as ammonia sulphate – a product which can be sold on as a liquid fertiliser.

The secondary scrubber unit works in a similar way to remove the acidic smell elements with the result that smells are diminished to acceptable levels.

The introduction of an in- vessel composting system on a national level could, says Mr Helme reduce the pressure on landfill sites and provide a more ecologically acceptable method of disposing of waste products.

"We plan to build an industry, not just a business," he says. "If all goes well I would expect to see composting units of this type being set up in other parts of the country, probably as a franchise or joint venture operation." &#42

From feathers to valuable fertiliser in four days. There are few signs of any feather material in the finished compost – only a rather strong smell of ammonia.

Bioganix boss Nick Helme with the in-vessel composter, which is fed with 20t of waste each day. Rotational speed of the unit is four revolutions an hour.

Drive for the composter cylinder is an electro hydraulic system which allows the slow rotational speed to be controlled.