Bennamann shares all about creating biomethane from slurry

That incident piqued my curiosity about the energy potential of organic waste. After some research, I discovered that China had experimented with millions of small-scale anaerobic digesters in rural villages back in the 1970s. The concept was simple but powerful - convert organic waste into usable biogas that could then be used for cooking and other energy needs.

Intrigued by the possibilities, my colleague Mike Bennett and I founded Bennamann in 2011. Our initial focus was on harnessing energy from grass cuttings. We calculated that one square metre of grass contains roughly the energy equivalent of one litre of petrol. Scale that up to a football pitch, and you're looking at around 5,000 litres worth of energy potential. The numbers were compelling.

However, our enthusiasm soon met a significant hurdle: storage. Grass grows abundantly in spring and autumn, but energy demand reaches its peak in winter. This mismatch posed a critical challenge to the viability of our concept.

Undeterred, we shifted our focus to solving this storage conundrum. Drawing on my background in physics, we began exploring innovative solutions, including the cryogenic storage of methane. This approach promised to bridge the gap between peak production and peak demand periods, revolutionising the way we think about grass as an energy source.

Bennamann smartcover modular system. (Image: Bennamann)

Slurry lagoons’ untapped potential

Our eureka moment came when we connected with dairy farmers and realised the immense untapped potential in slurry lagoons. Cows are remarkably efficient at extracting energy from grass, but a significant amount remains in their manure. What's more, the slurry is already broken down thanks to natural cow rumination and impregnated with anaerobic bacteria - nature has done half the work for us.

We developed our Smartcover system for slurry lagoons that captures the methane that would otherwise escape into the atmosphere. This seemingly simple innovation has cascading benefits for farmers and the environment.

Firstly, it dramatically reduces the farm's carbon footprint. The Intergovernmental Panel on Climate Change (IPCC) has shown that methane has a Global Warming Potential (GWP) of between 84-87 times that of carbon dioxide over a 20-year timeframe. This means that methane is significantly more potent than CO2 in terms of its impact on global warming over this period.

By capturing this fugitive methane, we can make a significant dent in agriculture's environmental impact.

Secondly, the cover increases nutrient density in the slurry by keeping out rainwater. In the South West, where we are known for high levels of rainfall each year, this means farmers can store up to 50% more slurry in the same space. This extended storage allows for more strategic application of this nutrient-rich digestate.

Chynoweth Farm, Bennamann HQ. (Image: Bennamann)

Increased crop yields

The benefits to soil health have been remarkable. Farmers using our system report being able to cut their artificial fertiliser use by up to two-thirds. The digestate is very easy to apply as it remains very fluid, and is more readily absorbed by soil, and plant root structures, leading to faster and more robust crop growth. One of our partner farms has seen an 80% increase in protein content in their silage as well as a visible rise in worm density- a game-changer for livestock, nutrition, soil regeneration and farm economics.

But the advantages don't stop there. By capturing and upgrading biogas to biomethane, we're providing farms with a renewable energy source. This can power farm equipment, including tractors and generators, creating a closed-loop system where nothing goes to waste. Due to this, we partnered with New Holland/CNH who have created the world’s first methane-powered tractor that perform on par with their diesel counterparts. Then in 2023 CNH became a majority shareholder in our business.

Mobile Biocycle. (Image: Bennamann)

A Modular Approach

We've designed our technology solutions to be modular and adaptable, catering to farms of various sizes, starting from around 100 cows. Our offerings can be scaled up as farms grow, ensuring that operations of all sizes can benefit from our innovations. We provide three different solutions to adapt to farm size and energy requirements:

1. Our Smartcover system, suitable for smaller and larger farms, provides immediate benefits in terms of slurry management and ammonia reduction to very low levels.
2. For medium-sized farms ready to capture and convert methane into energy, we offer biogas solutions that can be tailored to their specific needs.
3. Larger farms can benefit from our biomethane solutions, which are typically most efficient for operations with 300 cows or many more.

Using biomethane to power a tractor. (Image: Bennamann)

Energy Independence and Additional Revenue Streams

Regardless of farm size, we work with farmers to help find additional revenue streams through Government grants. For farms producing excess biomethane, we offer a service to process and sell this valuable resource, providing an additional income source. This approach not only promotes energy independence but also opens up new economic opportunities. The feedback from farmers has been overwhelmingly positive. Beyond the economic benefits, they're seeing improvements in soil health, reduced odour and a sense of pride in running a more sustainable operation. Many are approaching energy independence, dramatically reducing their input costs and simplifying their business model.

Looking ahead, we're continually refining our technology and exploring new applications. The potential for using grass and other vegetation as feedstock remains enormous, and we're excited about future developments in areas like fuel cells for even more efficient energy conversion.

At Bennamann, we believe we've hit upon a solution that transforms livestock farming from a perceived environmental problem into part of the solution. By closing the loop on farm waste and energy, we're helping create a more sustainable and profitable future for British farmers. The journey from exploding grass clippings to revolutionising farm energy has been extraordinary, and I'm convinced the best is yet to come.