The golden rule
Compare what you will actually get running at site (guaranteed CBG output, with your feedstock, at stated consumption), and the total cost to get there. A low equipment price with large exclusions is often the most expensive plant.
A. Technical checks
- Feedstock design basisIs it based on your lab-tested feedstock (solids, volatile solids, methane potential), harvest age and particle size? What happens to the guarantee if feedstock varies?
- Mass balance that adds upDoes the guaranteed CBG output fit within the methane the stated biogas range can deliver, even at the low end, after upgrading losses? Check with our yield calculator.
- Pretreatment adequacyFor straw or Napier grass, is there real fibre opening (shredding, milling, shearing), or only a chopper?
- Digester design & redundancyNumber of digesters, volume, retention time, material, insulation, mixing. One digester means no redundancy during maintenance.
- Upgrading option actually pricedIf water scrubbing and membrane are both described, which one is in the price? Compare power, water and methane-slip figures.
- Gas quality guaranteeMethane %, CO₂, H₂S, moisture dew point and pressure, aligned with BIS IS 16087 and OMC requirements. Ask for third-party test reports from operating plants.
- Utilities & consumptionPower (kW and kWh/day), soft/RO water, chemicals and media. These drive your operating cost for 20+ years.
B. Scope & exclusions
- Scope matrixFor every item: who designs, supplies, erects and commissions. Look for items marked "client".
- Battery limitsExactly where the supplier's scope starts and ends: feedstock inlet, power, water, gas outlet, FOM/LFOM outlet.
- Exclusions listCommon big exclusions: land and site development, civil works beyond the process plant, HT power connection and transformer, feedstock harvesting and storage, cascade vehicles, approvals, operators, insurance, GST.
| Often excluded | Why it matters |
|---|---|
| Civil works beyond process plant (bunkers, roads, sheds, boundary, drying yards) | Can be a large share of total project cost |
| HT connection, transformer & PCC | Needed before commissioning; long lead time |
| Feedstock harvesting, aggregation & storage | Decides whether the plant runs 330 days a year |
| Cascades, vehicles & dispensing | No CBG sales without them |
| Statutory approvals (PCB, PESO, fire) | Delays here delay revenue |
C. Commercial & contract terms
- Price breakup that totals correctlyEach line should add up to the stated total. Ask about any gap in writing.
- Payment milestonesHow much is paid before the plant performs? Link part of the payment to commissioning and the PG test, and ask for advance and performance bank guarantees.
- Performance guarantee testDuration, conditions, deemed-acceptance clauses, and remedies if guaranteed output is not achieved.
- Warranty, liability & delay damagesWarranty period for fabricated vs bought-out items, the liability cap, and whether delay damages are actually defined.
- Reference plants on the same feedstockVisit an operating plant using your feedstock type, and talk to its operator, not only the sales team.
Red flags that suggest a copy-paste proposal
Many offers are adapted from earlier projects. Small inconsistencies often reveal that the design was not really done for your site:
- Wrong project details: a different capacity, state, electricity tariff, feedstock or host industry (for example a sugar mill or distillery) than yours
- Contradictory technology: the same digester described as both "plug flow" and "CSTR", or an upgrading unit described as both "membrane" and "packed water scrubber"
- Numbers that don't agree: digester count or volume, compression pressure, or line items that don't add up to the stated total
- An off-spec product table: a CBG composition whose H₂S, CO₂ or moisture values would not pass IS 16087:2025, even though the text promises they will
- "Deemed acceptance" clauses: the plant is treated as having passed its performance test if testing doesn't happen within a fixed number of days, or if you start commercial operation first
None of these automatically disqualifies a supplier, but each one deserves a written clarification before you sign the purchase order.
How Biovardhan prepares a proposal
Every Biovardhan techno-commercial proposal starts from feedstock testing and a DPR-grade mass balance. It then defines scope, battery limits and exclusions in plain language, so you can see the full project cost. We cover the complete chain, from biomass pretreatment to digestate value addition. Request a proposal or send us an offer you already have, and we'll go through it with you.
Frequently asked questions
A complete offer includes the scope matrix (design, supply, erection, commissioning per item), mass balance, design basis, input and output specifications, consumption figures, equipment list with makes, battery limits, exclusions, price breakup, delivery schedule, payment terms, performance guarantee test, warranty and contract terms.
Mostly because of scope. Civil works, utilities, cascades, fire-fighting, laboratory, transformer, approvals and pretreatment are included by some suppliers and excluded by others. Compare the total cost of the full plant, not the headline equipment price.
A PG test demonstrates that the plant produces the guaranteed CBG quantity and quality with the specified feedstock and consumption. Check its duration, the conditions under which it is run, and what happens if the plant fails it.
Terms vary, but buyers usually protect themselves by linking a meaningful share of payment to commissioning and the successful PG test, and by securing advance and performance bank guarantees.