Turning Animal Waste into Fertiliser: Soil scientist Dr Gordon Rajendram on the Case for Composting

Every farm, orchard, and rural property deals with animal waste at some point: carcasses, offal, soft tissue and other organic residues that would otherwise be buried, burned, or trucked away at cost. For many landowners, this material is seen purely as a disposal problem. But according to Dr Gordon Rajendram, a growing body of research points to a better answer: composting.

Far from being a waste-management afterthought, properly composted animal waste becomes a stable, nutrient-rich soil amendment capable of genuinely reducing a farm's reliance on bought-in fertiliser.

The science behind this is well established. Sustained thermophilic temperatures above 55°C for several consecutive days denature residual protein and destroy the great majority of pathogens, a finding confirmed by peer-reviewed composting trials published in the Journal of the American Veterinary Medical Association and elsewhere. What goes in as raw animal tissue comes out as a biologically stable, humus-like product, with nothing recognisable as "waste" remaining.

Field research backs this up. In Hungary, composted animal processing waste applied at 20 to 50 tonnes per hectare improved yield and quality in maize, mustard and triticale crops, with benefits still measurable three to four years later. In India, recycled animal waste has even out-performed synthetic diammonium phosphate fertiliser in tomato field trials, supplying nitrogen as effectively as a manufactured product.

There is also a practical volume benefit. Composting typically reduces the initial mass of mixed waste and bulking agent by around 30 percent through moisture loss and organic breakdown, meaning significantly less material is left sitting on-site awaiting disposal at any given time.

The result is a genuine win-win: less waste accumulation, lower disposal costs, and a valuable soil conditioner supplying nitrogen, phosphorus, potassium and organic matter. Applied at agronomic nitrogen rates and to appropriate land, composted animal waste can replace or supplement synthetic fertiliser inputs.

For farmers, processors and rural advisors alike, the message is clear: composting animal waste is not a compromise or a stopgap. When done correctly, with proper temperature management and appropriate carbon-rich bulking agents, it is good agronomy, and a practical, evidence-based pathway that turns a disposal challenge into a productive on-farm resource.

For more information, please contact:

Contact Dr Gordon Rajendram

021 466077

rajendram@xtra.co.nz

www.gordonrajendramsoilscientist.co.nz

Contact Media PA

phillip@mediapa.co.nz

027 458 7724