Wet and sensitive residues
Pulps and other wet starch-production residues have limited storage stability. Their utilisation often depends on buyers, transport logistics and uninterrupted production processes.
Process solution for the starch industry
Biogas from starch pulp and starch production residues
Starch pulp, waste starch, waste gluten and other starch-production residues are converted through anaerobic digestion into biogas, biomethane, process energy and organic NPKS fertilisers.
Initial situation
Typical challenges with starch pulp and starch production residues
High process-energy demand
Starch-production plants require continuous electrical and thermal energy. Rising energy prices have a direct impact on production costs.
Nitrogen and sulphur compounds
Protein-rich pulps and gluten can lead to high ammonium and hydrogen sulphide concentrations in the digestion system and impair process stability.
Wastewater, odour and logistics impacts
Production wastewater, wastewater sludge, interim storage and residue transport generate additional costs and can constrain production expansion.
Process principle
From starch pulp and production residues to biogas and fertiliser products
Prepare the biosuspension
Pulps, waste starch, waste gluten, cleaning residues, filter dust, cleaning media and suitable wastewater sludge are combined with process water and high-dry-matter additives to form a pumpable biosuspension.
Aerobic hydrolysis
The biosuspension undergoes hydrolytic pretreatment with air at elevated temperatures. This opens up lignocellulosic structures and makes them accessible for methane formation.
Culture-retaining main digestion
The hydrolysate is fed to a hydraulically and only partially mixed main digester. A specialised culture adapted to protein- and lignocellulose-rich feedstocks is retained in the system.
Multi-stage anaerobic digestion
A robust mesophilic main digestion stage is combined with a downstream, preferably thermophilic post-digestion stage. This balances varying residue qualities, increases degradation and supports hygienisation.
Recover nutrients
The fermentation residues are separated into a solid fertiliser fraction and biofiltrate. Where required, ammonium and sulphur compounds are removed from the biofiltrate and recovered as liquid fertiliser concentrate.
Utilise biogas for energy
The biogas produced is desulphurised, dried and compressed where required. It can be used in particular for combined generation of electrical and thermal process energy.
Suitable feedstocks
Starch pulp, waste starch, gluten and other production residues
Starch-production residues
Pulps, waste starch, waste gluten, filter dust and residues from cleaning the raw materials used.
Liquid and sludge-type residues
Organically loaded cleaning media and sludge from on-site aerobic or anaerobic wastewater treatment.
Bioethanol-related residues
Press cakes from fermented mash and stillage from an upstream yeast fermentation and ethanol distillation process.
High-dry-matter additives
For example cereal chaff, mill dust, brushing dust and comparable lignocellulose-rich residues.
Client benefits
More value from on-site residue streams
Lower process-energy costs
The biogas produced can cover a substantial share of the plant's electricity and heat demand and reduce dependence on fossil energy sources.
Greater disposal security
The starch-production plant becomes less dependent on short-notice collection of wet pulps, fluctuating feed markets and external disposal routes.
Organic NPKS fertilisers
Plant nutrients are recovered in solid fertiliser fractions and liquid nitrogen- and sulphur-rich concentrates for further use.
Less wastewater, odour and transport
Integrating process water and wastewater sludge can reduce wastewater load. At the same time, interim storage, odour emissions and plant-related truck traffic are reduced.
Stable biological operation
Aerobic hydrolysis, culture-retaining digester technology and targeted inhibitor removal support stable treatment of protein- and lignocellulose-rich residues.
Potential for additional revenues
Surplus energy, marketable fertiliser products and verifiable greenhouse-gas reductions may, depending on the project and applicable schemes, create additional revenue potential.
Technical background
The process solution presented is based on German patent specification DE 10 2014 001 909 B4. The specific technical and commercial design must always be tailored to the project, site and material flows.
Project assessment