The engineering context
What the assignment needs to resolve
Feedstock security is a supply-chain assignment. The amount grown or generated in a district does not establish the amount that can be bought by a plant throughout the year. Farmers and suppliers may already have competing buyers, storage limitations, transport constraints or their own uses for the material.
The procurement plan therefore follows the material from source to digester. Quantity is recorded on an agreed wet or dry basis; sampling establishes the condition actually received; preparation and storage losses are recognised before assigning usable methane potential. For energy crops, cultivation, harvesting capacity and seasonal inventory belong in the same review as the agronomic yield.
Compare feedstocks on a consistent basis
| Material | Questions for the survey | Operating consequence |
|---|---|---|
| Napier and other forage crops | Harvest maturity, moisture, fibre, irrigation and collection schedule | Seasonal yield and handling effort can change together |
| Paddy straw and crop residues | Recoverable share, bale quality, grit, moisture and storage conditions | Preparation, wear and dry-season inventory need planning |
| Press mud | Factory season, competing outlets, ash and storage changes | A seasonal purchase plan must support year-round feeding |
| Cattle dung | Collection route, dilution, sand and actual daily recovery | Transported wet tonnes may overstate organic input |
| Source-separated food waste | Segregation, packaging, contamination and contractual acceptance limits | Reception and reject handling govern reliable utilisation |
Altpreneur scope
How we approach the work
Availability and competing demand
Map farms, dairies, mills and organic-waste sources. Check monthly supply, existing uses, supplier concentration and transport constraints instead of relying on district-level production totals.
Testing and process suitability
Define representative sampling for solids, organic content, methane potential and relevant contaminants. Review harvest age, fibre, grit and the pre-treatment needed by the proposed digestion process.
Storage and logistics
Plan receiving, weighing, rejection, seasonal buffers, silage or dry storage, drainage and loader movement. Include usable dry-matter losses and inventory finance.
Procurement controls
Develop supplier segmentation, quality acceptance, receipt records, pricing provisions and backup supply routes. Align contractual commitments with evidence of availability.
Decisions worth getting right
Measure delivered value
Compare the cost per unit of usable methane alongside cost per wet tonne. A cheaper, more diluted load can cost more to transport and process for the same energy output.
Size the inventory from the supply calendar
Storage is selected from the longest credible supply interruption, deterioration risk and replenishment plan. A fixed number of storage days copied from another project is not a procurement strategy.
Write quality into the agreement
Define weighing, moisture or solids assessment, sample retention, rejection, unloading responsibility and price adjustment. The plant must be able to apply those terms at reception.
Assignment outputs
What you receive
- Feedstock catchment and supplier assessment
- Monthly availability and procurement-cost model
- Sampling and acceptance protocol
- Storage and transport strategy
- Supply-risk register and procurement roadmap
To begin
Useful starting information
- Plant location or candidate areas
- Preferred feedstocks and any existing supplier contacts
- Target operating hours and preliminary capacity, if known
Scope and responsibility
Third-party supply commitments and laboratory results must be confirmed separately. Crop yield and methane yield remain dependent on actual agronomy, material quality and plant operating conditions.
Common questions
Is leased Napier acreage sufficient evidence of feedstock security?
No. Irrigation, harvest yield, seasonal variation, cutting schedule, transport, losses and alternative demand also need examination.
Should we buy only on wet tonnes?
Wet tonnes alone can hide moisture and contamination differences. Quality measures and usable organic content should inform the acceptance and commercial basis.
Evidence & further reading
Source material
- IEA: Sustainable potential and cost of biogas feedstocks
- Koch et al. (2020): Power and limitations of biochemical methane potential tests
- US EPA AgSTAR: Project Development Handbook
Technical references inform the discussion. Final design, operating limits and policy eligibility depend on the project and applicable current documents.