Straw briquettes: crop residue becomes biogas

India burns millions of tonnes of paddy straw in the fields every year. Kinetic Biofuel, part of the Danish press manufacturer C.F. Nielsen, has developed a mechanical process that turns this straw into a high-yield substrate for biogas and BioCNG plants.

How it works Ask for a straw study

At a glance

250≈250 Nm³ CH₄ per tonne strawup to ≈300 under optimal conditions→10×absorbs 10–12× its weightbriquettes sink and spread evenly→75≈75 kWh per tonne strawpress energy, recovered as heat→3three press sizes0.6 to 2.8 tonnes per hour→

01 How it works

Compression and pre-treatment in one step

An eccentric press forces straw through a conical die. Pressure and friction open up the straw structure, so water, microorganisms and enzymes reach the fibres. No steam, no chemicals, no water are needed.

Bales

Straw bales are opened and fed to the straw line.

Cleaning

The straw line removes stones, soil and sand, protecting the press and the digester.

Briquetting

The press compresses and pre-treats the straw; little air remains in the briquette.

Feeding

Briquettes go straight into the reactor by screw feeder or via a mixer tank.

Sponge effect: soaked briquettes reach the density of water, no floating covers or sediment
No impact on hydraulic capacity: dry briquettes, no extra slurry or tanks
Press energy is recovered as process heat when the press stands at the plant
Less nitrogen and oxygen in the biogas, which helps upgrading to BioCNG
Helps against ammonia inhibition; allows co-digestion with poultry manure
Demonstrated for more than three years at Aarhus University’s Foulum facility

02 Yields

How straw pre-treatment compares

Pre-treatment	Methane yield (Nm³/t straw)	Max. straw in slurry	Extra methane per t slurry
Shredded straw	200	1–2 %	10–20 Nm³
Other mechanical processing	225	2–6 %	27.5–67.5 Nm³
Briquetted straw	250	8–12 %	100–150 Nm³
Briquetted with catalyst	300	10–12 %	150–180 Nm³

Reference: at Farm Renewables on the Isle of Sheppey (UK), straw briquettes deliver nearly half of the plant’s total biogas.

Manufacturer figures, Kinetic Biofuel / C.F. Nielsen.

03 Presses

Three mechanical briquetting presses

Robust eccentric presses from C.F. Nielsen. Capacity depends on the raw material and the briquette density: briquettes made at the biogas plant can be looser (more capacity), briquettes for transport are made harder.

Model	Capacity	Typical use
BP 4000	0.6–0.7 t/h	Smaller plants
BP 6510	1.4–1.7 t/h	Most popular model
BP 7510	2.2–2.8 t/h	High-capacity lines

Photo: BP 6510 pressfrom Kinetic Biofuel (permission requested)

04 Integration

At the biogas plant or at the straw source

Press at the biogas plant

Looser briquettes, higher press capacity, no briquette storage. Briquettes go directly into the digester by chain conveyor and screw feeder, or are stirred into slurry in a mixer tank and pumped.

Press at the farm or collection point

Harder briquettes for transport and storage. One briquetting line can supply one or several biogas plants and cuts transport volume compared with loose bales.

05 For India

From stubble burning to BioCNG

Paddy straw is plentiful, cheap and today largely burnt in the field. Briquetting turns it into a reliable substrate for CBG plants under the SATAT programme and for existing biogas plants that want to grow without more manure or food waste.

Feasibility study with your straw quality and plant data
Supply, installation and commissioning by Bert Energy India
Service and spare parts from India, backed by the manufacturer

Ask for a straw study

Video: straw briquette explainerfrom Kinetic Biofuel (requested)

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