Peter Swann, Sunnydale Alpacas
A little while ago, I was asked to help out on a research project to tackle a problem of manure at a large equestrian operation. Large quantities of strawy stable manure were being produced and composted. Taking up to a year to fully break down, the quantity being held, and the risk of rain water run-off getting into local water courses, was drawing the unwanted attentions of the Environment Agency. Something had to be done.
The company I was helping in coming up with a solution, Biotechnical Energy Ltd of Okehampton in Devon, manufactures machines primarily aimed at the waste food sector. However, the technology could be applied to any organic material. The machines work by taking in the organic waste, churning it to add air, warming it up and adding in specialist high temperature bacteria. Those bacteria break down the cell structure of the organic material, releasing the moisture and turning the waste into a dry crumb. And it all happens within 24 hours.
The process can be continuous, or carried out in batches. The residue, coming out after treatment is called digestate, and looks a little like dried coffee grounds. It has some interesting properties, which can be summarised as:
Reduced Waste Disposal Challenges. If the waste is to go off to regular disposal routes, there are many advantages to processing it first. The digestate shows a reduction of up to 80% in both weight and volume from the original input. Because it is dry and odourless, there is no attraction to pests, such as flies, wasps, rodents etc. and it can easily be stored in dry conditions.
Soil Conditioning. In this particular project, the client was keen to get the nutrient value of the waste output back into the land. They had been shipping out the fully composted stable manure to local farms where it was ploughed into arable land. It meant a slow degrading of the mineral content of the soils on the farm, which had to be made good with expensive fertilisers. They had considered spreading the composted manure on their own pastures, but the risk of raising the worm burden on the ground and of spreading such organisms as e-coli, had prevented that option.
Examples of the fresh stable manure were run through Biotechnical Energy's own test machines. Samples were taken at various stages during the processing and sent to two laboratories for chemical and biological analysis. The results were astounding. Table 1 shows the pH of the final product is neutral, and the mineral content is definitely worth having back on the sward, especially as it is ?Free?. The biological tests were even more impressive, the high temperature and bacterial action taking place within the machine totally destroyed all worms, worm eggs and pathogenic bacteria within the first hour of an 18 hour process. See table 2. The clients vets were completely sold on the concept of putting the manure through the Biotechnical Energy machine and spreading onto the pasture the following day.
Approved Biomass Fuel. The dry crumb has excellent characteristic as a biomass fuel. It's calorific value is higher than wood, and nearly as high as coal. It burns with a hot flame. Typically, it can be added to wood pellets and burned in a suitable pellet burner. In many cases, the heat produced will qualify under the governments Renewable Heat Incentive scheme with substantial financial rewards for committing to the reduction in use of fossil fuels.
As the owner of my own alpaca herd, I instantly recognised the potential to the mid ? large equestrian or alpaca operation. Like many others, I have a paddock cleaner, so I have a regular supply of manure. Like many other farms, I have plenty of other other organic material that I have to dispose of, from kitchen waste to weeds from the veg patch and the muck from my hen-house. It can all go in. The smallest unit that Biotechnical Energy manufacture is the BeD200 which takes up to 200 Litres per day of organic waste and costs around £18,400. So if I put in 200 Litres of waste, and achieve the sort of results that are typical for strawy manure, I could expect around 100kg of digestate. This output can go safely straight onto my fields, with the certainty of complete pasteurisation of pathogens and worms. Poo picked today, can be safely returned to the fields tomorrow. Alternatively, especially in the winter, that 100kg of biomass fuel will generate about 450kwh of heating, which would replace about 40 litres of heating oil.
Biotechnical Energy also produce larger machines that can take up to 5 tonnes a day of organic waste, but these are aimed at larger scale operations such as hotels, supermarkets, food factories and similar. The smaller unit described above is aimed at mid -sized restaurants, or anybody who produces more than about two or three wheelie bins of food waste a week.