Crude oil was known as black gold in the old economy but in the circular economy there’s a new Black Gold. A pretreated liquid feedstock which is the food for Anaerobic Digesters and the source of green biogas.

AD feedstock pretreatment is fast emerging as one of the most impactful additions to the Anaerobic Digestion (AD) & biogas production process. Releasing more gas per tonne of feedstock and boosting profits accordingly.

“It’s the AD equivalent of taking a pre-workout sports drink and doing a warm-up” according to Alps Ecoscience’s Technical Director, Wade McRoberts. “The uplift in digester performance is so significant it can change the business model for many operators.”

The principles of biogas feedstock pretreatment

The effort upfront to prepare feedstock’s properly greatly enhances the performance and stability of the digester. Leading to increased methane release, and more complete digestion. This enhanced digestion reduces the volume of residual solids to be managed. Whilst also enhancing liquid digestate nutrient quality and boosting its commercial value.

The primary impact in gas yield can be measured in thousands of pounds of additional daily revenue. With results coming on stream within a few weeks. Uncapped gas to grid AD plants can potentially achieve a big profit uplift for minimal investment. Sites with fixed output capacity can do the same through savings in feedstock purchases & haulage.

There are a number of processes, that when used in combination enable Alps Ecoscience to deliver the rich, black substrate soup which is the optimal feedstock for efficient anaerobic digestion. These involve specific sequences of macerating, stirring, heating, pressuring and catalysing in order to provide a homogenous solution receptive to hydrolysis and acidogenesis. This patented process is called SMASH and is individually engineered for optimal results.

The SMASH pretreatment process overview

The start point in feedstock pretreatment is always a feedstock classification study. This determines the optimal pretreatment protocol for the digester configuration. Highly lignocellulosic feedstocks, require different treatment sequences and intensity to break open the fibres and unlock their full bio-energy potential.  For crops like maize, hydrodynamic cavitation (HDC), which in the use of pressure variance within a liquid to create and then collapse bubbles proves highly effective. The resultant HDC micro shock waves have destructive effects on solids in dispersions, emulsions and slurries affecting particle size and distribution. The forces within these waves are such that they can break down any solid fibrous materials within the solution. Hydrodynamic cavitation also increases the surface area between insoluble liquid reactants, accelerates dissolution and disaggregates particles. When employed in anaerobic digestion, HDC equipment breaks down recalcitrant materials into a flowing mass, aiding microbiological access to the cellular juices.

This access to the sugars and starches within the material enables the use of high lignin feedstocks and the efficient amalgamation of mixed sources of food waste. When combined with warming, resting and catalysing stages the feedstock quickly becomes the homogeneous, smooth dark liquid you see below. The biogas equivalent of crude oil optimised for rapid anaerobic digestion which maximum volatile solid (VS) utilisation and gas release.

For some feedstock, increasing mechanical agitation is sufficient but for other more complex protein mixes, addition of a specific catalyst and nutrients pay dividends once they transfer into the reactor. In the correct combination Alps Ecoscience SMASH solution is yielding more complete digestion in a shorter period than where AD feedstocks are not pre-treated. In fixed capacity AD plants this makes a material difference to revenue through feedstock optimisation. Producing more gas from the same feedstock volume at a faster rate when stocks are plentiful or reducing the organic loading rate when looking for savings. Typically, on standard size plants, operators can expect £3,000 to £5,000 per day in incremental revenue.

Biogas process innovation through research

SMASH is the culmination of 5 years of research and development by Alps Ecoscience into feedstock preparation and digester performance. When Managing Director, Mike Platt, entered the industry he was stuck by how capital intensive it was and driven by return on assets. He commented.

“In an industry where you can’t build a bigger tank or churn the substrate faster without incurring significant cost. There had to be a way of realising more energy from the feedstock. That has been our focus and with our innovations in feedstock preparation, we can now offer a way to boost biogas plant profit with minimal investment. ”

To understand how SMASH pre-treatment technology can improve your feedstock digestion to increase gas output and profits please contact Business Development Manager, Trevor Johnston, trevor@alpsecoscience.co.uk.