Process engineering is our deepest capability.

Anaerobic digestion, biogas and biomethane plants live or die on the process. Redrock designs, sizes and troubleshoots them from first principles: mass and energy balances, reaction kinetics, unit-operation design and hazardous-area engineering, grounded in how the biology actually behaves. This runs through every project we develop.

The flow sheet

The unit operations we design.

Reception & pretreatment

Weighbridge, enclosed reception, depackaging, maceration, screening and buffer storage. Sized around what actually arrives, including contamination and grit, not a clean design feed.

Pasteurisation & hygienisation

Batch or continuous pasteurisation to the animal by-products rules, 70°C for one hour at a maximum 12 mm particle size, with heat recovered back into the process.

Digestion

Mesophilic or thermophilic digestion, single or multi-stage, sized on retention time and organic loading and stabilised around the microbiology, not the equipment datasheet.

Gas handling & conditioning

Biogas collection, hydrogen sulfide removal, drying, and gas storage, engineered for a safe, steady feed to upgrading or CHP.

Upgrading to biomethane

Removing carbon dioxide to grid specification by the route that fits the site: water scrubbing, PSA, membrane, amine or a metal-organic-framework sorbent.

Digestate & nutrients

Separation, dewatering, concentration and nutrient recovery, turning digestate into a compliant product rather than a disposal liability.

Sizing & balances

The numbers that set the plant.

A digester is sized on hydraulic retention time and organic loading rate, then checked against mixing power, heat demand and the biology's tolerance for ammonia, volatile fatty acids and sulfide. We build the mass and energy balance that ties feedstock, gas yield, heat and power together, so parasitic load and net export are known before anything is ordered.

Heat integration is where margin is won or lost. Pasteurisation heat, digester heating and upgrading demand are recovered against CHP and process streams, so the plant runs on its own energy wherever it can. Scale-up from bench and pilot BMP data to full scale is done with the same discipline, not by extrapolation.

Upgrading

Biogas to grid-quality biomethane.

There is no single best upgrading technology. The right choice depends on scale, the gas market, the site's power and heat, and the tolerance for methane slip. We specify across the full set.

Water scrubbing

Robust, water-only, well understood. Higher parasitic power and footprint, no chemicals.

Pressure swing adsorption (PSA)

Adsorbent beds cycling on pressure. Compact and dry, with methane slip to manage.

Membrane separation

Selective polymer membranes, modular and low-maintenance, sensitive to gas conditioning upstream.

Amine scrubbing

Chemical absorption for very high methane recovery and very low slip, at a heat cost.

Metal-organic framework (MOF)

A high-selectivity sorbent route. Redrock holds a licence to a MOF-based upgrading technology, a distinctive option in our toolkit.

To market

Grid injection or virtual pipeline.

Where a grid connection exists, biomethane is conditioned and metered to network specification for injection. Where it does not, we design the CNG virtual pipeline: compression to around 250 bar, cascade filling, multiple-element gas containers for road transport, and the decompression and metering skid at the receiving end.

Both routes are engineered to the hazardous-area rules from the outset, with ATEX zoning, gas detection and the transport code requirements built into the layout rather than added afterward.

Safety by design

P&IDs, HAZOP and hazardous-area engineering.

Biogas is flammable and plants handle it at pressure. Safety is engineered in, not bolted on: process and instrumentation diagrams, HAZOP and LOPA studies, ATEX and DSEAR hazardous-area classification, relief and blowdown, and the control and shutdown philosophy. The result is a plant that is safe to operate and straightforward to permit.

Reg 1069/2009 (ABPR) VDI 4630 ATEX 2014/34/EU DSEAR HAZOP / LOPA EN 16723 (biomethane) CNG virtual pipeline

Have a plant to design, or one that isn't performing?

From a flow sheet on a new project to troubleshooting an existing digester, let's talk about the process.

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