Build a useful source assessment by connecting process origin, measurement basis, variation, contaminants, product acceptance and utility interfaces.
The first question is where the recovery plant begins
A source assessment identifies the gas available at the proposed equipment inlet. That sounds simple, but many early inquiries mix information from different points in a process. A raw-biogas flow paired with the concentration after upgrading does not describe a real stream. Nor does a fermentation gas analysis necessarily represent the gas after it has passed through a shared collection network. Start by marking the sample location and proposed battery limit on a simple diagram.
Record the upstream process, its normal inputs and the changes that can affect the gas. This gives the analytical work a purpose. A laboratory can only report the compounds included in its method; it cannot infer every possible contaminant from the bulk CO₂ percentage. Process knowledge helps the project team select a representative analytical program.
Build one consistent measurement basis
Record minimum, normal and maximum flow, the meter location and whether the result is mass flow or gas volume. For volume measurements, include reference temperature, absolute pressure and wet or dry basis. Keep the CO₂ concentration on the same basis. If these values come from different instruments or dates, reconcile them before calculating available CO₂.
A concentration expressed in volume percent is not a mass fraction of the total mixture. To convert a measured gas volume to CO₂ mass, use the appropriate gas relation and molecular mass, or a validated property method for the conditions involved. Do not apply a concentration correction again if the measurement already reports kilograms of CO₂ rather than kilograms of mixed gas.
Measure variation as well as an average
A single sample can establish what was present at a particular time. It does not establish the full operating envelope. Consider start-up, steady operation, shutdown, changes in feedstock or fuel and source maintenance. For batch operations, align the gas-quality and flow records with the production cycle. For a shared header, understand which sources were contributing during sampling.
This time dimension affects both collection and processing. A plant may have enough annual gas but insufficient supply during a customer’s peak demand. A brief high flow may require buffering or a deliberate decision not to recover the entire peak. The design basis should state which conditions are required duties and which need isolation or another agreed response.
Connect each contaminant to a decision
The useful output is a contaminant-to-treatment matrix. For each relevant compound, identify the measured or assumed inlet range, required product limit, proposed treatment stage and verification method. Mark unknown values explicitly. Some unknowns affect equipment size; others affect whether the proposed product market is appropriate at all.
Food and beverage use requires a broader discussion than a purity headline. ISBT’s public resource catalog identifies guidance covering feed-gas considerations, finished-product impurities and analytical methods. Obtain the applicable customer specification and current documents for the actual project rather than treating a reference link as certification.
Turn the assessment into a useful inquiry
A productive inquiry combines six items: process origin, representative analysis, flow profile, operating calendar, target product specification and site utilities. Add the intended delivery form and customer demand so storage and commercial offtake can be considered. Label preliminary estimates and identify the person or test that can resolve each important gap.
We can then discuss a recovery route on a defined basis: where collection starts, which treatment duties are required, what the liquid or gaseous product must meet and which site interfaces are included. The purpose of this stage is not to make every uncertainty disappear immediately. It is to expose the decisions that must be resolved before a capacity or quality guarantee becomes meaningful.
Common technical questions
Is a high CO₂ percentage enough to start a guaranteed quotation?
It is useful initial information, but it does not establish trace-contaminant treatment, operating variation, product acceptance or the measurement basis.
What is the most useful first document?
A concise design-basis sheet with a stream diagram, dated measurements, the product specification and clearly marked unknowns helps the engineering team identify the next decisions.
A sample request that avoids a misleading quotation
| Information received | Why it is insufficient | What we ask for instead |
|---|---|---|
| 2,000 m³/h biogas; 98% CO₂ | Flow may refer to raw biogas, while composition refers to an upgrader outlet. | Flow and composition measured at the same CO₂ recovery inlet, on one wet/dry and pressure basis. |
| One sample during stable production | It may miss start-up, cleaning or feedstock changes. | A sampling plan covering normal operation and known variations, with dates and process status. |
| Food grade required | No agreed individual impurity limits or release method. | The intended market, customer specification, source acceptance and analytical methods. |
An unresolved inlet definition is a reason to request measurements before selecting a compressor. An unresolved customer specification is a reason to keep the quality scope open. Neither is solved by adding an arbitrary percentage to the nameplate capacity.
Technical references
- ISBT: Bulk Carbon Dioxide quality and analytical guidance, publication BVG-00001 — The publication covers feed-gas considerations, finished-product impurity levels and analytical methods. The copyrighted publication itself was not reproduced.
- EIGA: Food and beverage gases — Industry context for food and beverage gas applications.
- US EPA: Renewable natural gas from agricultural anaerobic digestion — Biogas upgrading removes CO₂, water, hydrogen sulfide and other impurities to increase methane content.
- ISBT: Biogenic Carbon Dioxide—Ethanol Fermentation vs. Anaerobic Digestion, BVG-00004 — ISBT lists a December 2025 comparison of these feedstock routes; it does not make all biogenic sources automatically suitable for beverage use.
Apply this to your project
Open the source assessment tool to record the mass-balance and economic assumptions. For a project-specific design, share the gas analysis and product specification with us.
We publish this guide as YTC. Our editorial policy explains the source checks, AI assistance and how to report a correction. Examples do not establish a plant guarantee.