Novel manure processing options for poultry producers

Capacity for this trial is anticipated to accommodate around half a million layers’ manure, but this is a scalable enterprise. Photo: Canva

Newquip, the UK distributor for Big Dutchman, has been working with a poultry producer to produce a high quality fertiliser from raw poultry manure.

Poultry producers are increasingly facing tougher restrictions on the use of muck on their land due to mounting concerns about nutrient imbalance and environmental harm to rivers and the imposition of Nitrate Vulnerable Zones regulations. The pressure is driving the industry to invest in methods to process manure.

Until now, poultry manure is stored ready for application to land to help the next cereal crop, but conscious of the diminishing capacity for soil indices to continually accommodate muck, the farmer – who wished to remain anonymous – wanted to add value by improving its consistency and reducing moisture content. This is because muck in August is very different from muck in December.

Converting manure

The aim of the farm trial, highlighted in the Ranger magazine, is to convert manure from a useful byproduct for those with access to sufficient land and crop demand, to a consistent and high-quality alternative to conventional chemicals.

Adam Dye, Newquip managing director, said: “The finished product should match all of the benefits of using chemical fertiliser. Crucially, it must be consistent and stable so that application to land can be made accurately. It needs to be readily transportable and storable, odourless and inert.

The building is comparable in size to a large poultry shed, some 120m in length with higher elevations providing a 4m drop from raw material intake to finished goods dispatch, plus the all-important airspace to create a plenum – an aerobic chamber where the composting will happen.

The manure of half a million layers

Commissioning is expected in late 2024, and the contractors are currently mid-way through the building phase. The unit itself is deliberately sized, with the farmer having taken guidance on animal byproduct and waste management legislation. Capacity for this trial is anticipated to accommodate around half a million layers’ manure, but Dye stresses that this is a scalable enterprise.

“This concept is entirely scalable with potential to aid existing farms by adding value to manure. It’s relevant to any future farmers, providing a solution for planning legislation whilst improving arable soils’ organic matter with associated benefits and reducing emissions from agriculture,” he noted.

The size means it’s necessary to purchase raw manure from local farms, but with an ambition to produce a premium finished fertiliser, the specification of muck on arrival will need to be managed. For a start, only manure from belts will be accepted, minimising foreign objects and increasing consistency.

The process

Biosecurity measures upon arrival include a large wheel wash and curtain spray system, with accompanying filtration and storage tanks. Vehicles then tip to a hopper, crossing over a weighbridge on the way in and out.

Manure is then blended with a biomass, providing structure, improving stability and feeding the all-important microbials. The mixture is deposited on long, elevated platforms and the process of aeration begins. Over a fortnight, the mixture is dried, oxygenated and continually agitated by robotic cultivators in the plenum. The temperature target is around 65 degrees, sanitising the mixture of pathogens but protecting the microbes. The end result is a compost with around 80% organic dry matter.

At this point, further moisture is removed in the pelletising process with a targeted 95% dry matter content, ready for storing and shipping.

Environmental features

Among the environmental features are ammonia scrubbing, heat recovery and recirculation, rain water harvesting and wash water recycling. 800kw of biomass boilers are used to top up the recovered heat needed for drying raw material, improving consistency, or pelletising the finished product, while 500 kW of roof-mounted solar panels cater for the majority of the electrical load.

As with air scrubbers, now commonplace on extensions and new farms, sulphuric acid is a byproduct. Extensive critical control measures including bunding, specialist piping, limited and secure access, isolation and monitoring mechanisms are in place. Potash is used to neutralise surplus acidity, reducing the carbon dioxide emissions of alternatives such as pig slurry or sodium bicarbonate, and creating a secondary valuable output for fertiliser.

Through the mitigation of traditional soil conditioners and the emissions associated with spreading the raw muck, calculations suggest the process will offset the carbon dioxide emissions equivalent to several million trees annually.

Academic evaluation

The farmer and Newquip have enlisted the support of academic research and development, evaluating their ambitious hypotheses. Results from a study by Teesside University in England are due later in the summer. The hope is that their findings validate the efficacy as a fertiliser, and help better understand the symbiotic microbial relationships between nutrient and beneficiaries. Scientific results will help break down the barriers to use in arable farming.

Contact has been made with several industries; fresh produce, premium horticulture, top fruit, mushroom and viticulture firms are already interested, and awareness through agronomists and farm advisors is being built.