The Renewable & Low Carbon Energy website for agricultural and rural communities

Feedstock Preservation – The Key to Improved Biogas Production

Case Studies

Even with the most advanced AD plant and the best engineers, without the right feedstock management system your biogas plant will never reach its full potential. Maximising performance and efficiency should begin with the forage feedstock preservation, where dry matter losses of ensiled energy crops have a huge effect on lowering biogas production and, thereby, profits.

Trials show that, in the UK, the average dry matter loss from ensiled forage is around 25%. It would be unthinkable in any other business to write off a quarter of the stock, so why accept it in the biogas industry?

Understanding Dry Matter Losses

Feedstock preservation - Understanding Dry Matter Losses

Dry matter losses come from the most digestible part of the feedstock, leaving a greater proportion of non-digestible matter behind which, in turn, can have a negative impact in the digester. With losses primarily in the form of carbon dioxide and water, not only is the energy value of the silage reduced, the release of carbon dioxide is adding to the carbon footprint.

Making the right choices to preserve the feedstock’s potential is crucial to the performance of any AD plant.

Newly launched AD Feedstock Solutions, part of Kelvin Cave Limited, brings 40 years’ experience in the field of forage preservation and clamp management, with a focus solely on the AD industry. The company works with customers to devise bespoke feedstock management solutions.

They state there are three key areas to consider in order to minimise dry matter losses and optimise biogas production:

  • Preservation
  • Compaction
  • Protection

Preservation

Treating the crop with an effective preservative that destroys all undesirable microorganisms, will ensure the rapid pH drop required for an efficient fermentation, minimising dry matter losses and guaranteeing long-term aerobic stability. In independent trials Safesil, a unique preservative for all types of forage crops, is proven, when used as part of a complete clamp management system, to achieve this.

Compaction

It cannot be underestimated how important compaction is when filling the silage clamp. Fermentation is an anaerobic process, so it is important to remove as much air as possible from the clamp. A SilaPactor, available from AD Feedstock Solutions, can increase consolidation by up to 40%. A density of 750kg/m3 should be the minimum level to aim for in order to help prevent aerobic spoilage and reduce dry matter losses.

Protection

The clamp should be sealed as soon as consolidation has been completed. Remember, anywhere where the sheeting is not touching the forage is an air gap. It is not good enough just to be an oxygen barrier, the sheeting needs to mould to the silage to prevent air pockets. For the best results O2 Barrier 2in1 sheeting should be used, combining both a thin vacuum layer and a top polyethylene layer, applied as one sheet.

Feedstock preservation - How the O2 barrier works

As the maize harvest fast approaches, make sure you take steps to retain as much of the value of this energy rich crop as possible – don’t waste the energy you’ve already paid for.

More information on AD Feedstock Solutions, including their contact details, can be found here.

Related

Latest in Advice & Opportunities