Slurry management using separation technology

On-FarM manure management has received growing scrutiny in recent years due to the potential for pollution associated with some poor management practices. Slurry management can pose numerous challenges to farmers, as the infrastructure required to contain or house this material can be costly, and the size of the slurry burden can be difficult to predict.

Implementing management practices that reduce the potential for the production of slurry material is best practice for reducing the burden of storage and application.

On-farm infrastructure should avoid mixing rainwater into the slurry resource, as this will increase the space required for storage. Therefore, improving on-farm infrastructure to avoid this effect (i.e. by putting roofs over cattle yards, or improving guttering and drainage) is an essential strategy.

Utilising separation technology also offers several benefits. Slurry can be separated into solid and liquid fractions through the removal of solid organic or inorganic material from the liquid manure.

The resultant solid fraction is primarily composed of dry matter rich material, which contains the majority of the organic matter, including a significant proportion of the phosphorus. The liquid fraction is primarily water and nutrient components such as mineral nitrogen and potassium. The constituents of each material will depend heavily on the technology used during the separation process.

There are several approaches for slurry separation. Mechanical separation typically involves the use of apparatus such as a press, screen or centrifuge. Mechanical separators are efficient in producing a solid fraction with a high total solids content, on a relatively cost effective basis.

For example, one study showed that a screw press can recover as much as 73 per cent total solids when separating solid and liquid fractions. In addition, microfiltration or electrolysis approaches can be highly effective as separation systems, offering potentially greater control over the composition of the end products.

One alternative technology for slurry separation, currently under investigation at Coleg Sir Gâr, uses a process known as sonoelectrochemistry, which combines ultrasound and electrolysis to separate the different fractions.

Separation technologies offer great potential to reduce the burden on farm infrastructure of managing farm slurry output and resource. By separating this material into solid and liquid fractions the requirement for organic waste storage can be reduced, the resultant material can be easier to handle and transport, and the potential for environmental pollution is reduced.

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