Reporting RECD Outcomes in ESG Disclosures: Which Metrics Should You Use?

The sustainability team sends the plant engineer a one-line email: “We fitted RECDs on our generators this year. What number can we put in the report?” The honest reply is not one number. It is a short list of numbers, each with a different level of reliability, and the job of RECD ESG reporting is to pick the ones that will survive an assurer’s questions.

Some RECD outcomes are counts you can defend line by line. Others are estimates that hold up only with a disclosed method. A third group sounds impressive but rests on assumptions that are hard to justify for a fleet of diesel generators.

This post is organised as a metric menu. Tier 1 metrics you can report confidently. Tier 2 metrics need method notes beside them. Tier 3 metrics should be avoided or caveated heavily. A worked example, a data-quality checklist and sample wording follow.

Where RECD outcomes sit in ESG frameworks

Two frameworks decide where the numbers land for Indian listed companies with DG sets.

BRSR air emissions disclosure (other than GHG)

SEBI’s Business Responsibility and Sustainability Reporting circular of May 2021 made BRSR mandatory for the top 1,000 listed companies by market capitalisation from FY 2022-23. Under the environment principle, the format asks for details of air emissions other than GHG emissions. Published BRSR reports show this table listing NOx, SOx, particulate matter (PM), persistent organic pollutants, volatile organic compounds, hazardous air pollutants and an “others” row, with the reporting entity asked to specify the unit.

That “specify the unit” instruction is important. There is no single prescribed unit, so companies report PM in tonnes, kilograms, mg/Nm3 averages and more, which makes year-on-year comparison fragile unless you state your basis clearly. SEBI has also introduced BRSR Core, a subset of indicators that carries third-party assurance requirements on a phased basis. Whether air pollutant rows fall inside the assured subset for your company and year is something to confirm with your company secretary or assurance provider, because the framework has been revised more than once.

RECD outcomes belong in, or alongside, the PM row and in the narrative on air pollution control. They are not a GHG item.

GHG Protocol Scope 1: the RECD does not change the calculation

Under the GHG Protocol Corporate Standard, direct emissions from sources a company owns or controls are Scope 1. Diesel burned in your own DG sets is stationary combustion, so its CO2 is Scope 1, calculated from litres of fuel consumed multiplied by an emission factor.

An RECD does not alter that arithmetic. It does not reduce fuel burned, and the small back-pressure effect, if anything, nudges fuel use slightly upward. We work through the carbon mass balance in detail in our post on whether an RECD reduces CO2 emissions, so this article will not repeat it. The short version for reporting: keep the RECD out of your Scope 1 figure entirely, and do not let anyone describe it as a carbon project.

How the RECD ESG reporting metric menu works

The tiers are based on two questions: how directly is the number observed, and how many assumptions sit between the observation and the claim?

Tier	Meaning	Typical metrics	Disclosure approach
Tier 1	Directly counted or measured; few assumptions	Coverage, compliance test pass rate, verified PM reduction %	Report confidently, with the evidence filed
Tier 2	Calculated from measured inputs plus a stated assumption	Estimated PM mass avoided, PM emission intensity, maintenance KPIs	Report with a method note and assumptions
Tier 3	Relies on contested conversions or factors outside your control	Black carbon or climate equivalents, health outcomes, CO2 or NOx reductions	Avoid, or caveat heavily and keep out of headline figures

The tiers do not rank importance. Health benefits matter enormously; they simply cannot be quantified credibly from a company’s own DG data.

Tier 1 metrics: report these confidently

Tier 1 inputs are records you already hold, the formulas are simple, and an assurer can trace every number to a document.

Coverage: share of DG capacity and run-hours fitted with type-approved RECDs

Definition. The proportion of your diesel generator fleet that is fitted with a CPCB type-approved RECD that is installed, commissioned and in service at the period end.

Data sources. Asset register, commissioning reports, type-approval certificates, run-hour meter readings or controller logs.

Formulas. Report coverage three ways, because each tells a different story:

• By count: fitted sets ÷ total sets in scope × 100
• By capacity: fitted kVA ÷ total kVA in scope × 100
• By run-hours: run-hours on fitted sets ÷ total DG run-hours × 100

Run-hour coverage usually matters most for air quality: a fitted standby set that ran 20 hours matters less than an unfitted set that ran 600. Metered kWh per set gives an even better weighting.

Pitfalls.

• Counting devices that were delivered but not commissioned by the period end.
• Counting a device whose type-approval does not cover that engine rating. Our guide on checking that an RECD is CPCB tested for your DG set explains how to match certificates to engines.
• Leaving the scope undefined. State whether rented sets, sets above the procedure’s 800 kW engine limit, and sets at tenant-controlled sites are included.
• Estimating hours from memory instead of meter readings. Our post on using DG load logs shows what good records look like.

Compliance: emission tests passed versus tests conducted

Definition. Of the stack emission tests required under your consent conditions, SPCB directions or internal standard during the period, how many were conducted and how many met the applicable limit or reduction requirement.

Data sources. Test reports from the laboratory, the sampling plan, consent conditions and your compliance calendar.

Formula. Report two figures together: tests conducted ÷ tests required, and tests passed ÷ tests conducted. Showing only the pass rate hides missed tests, which is exactly what a reader most wants to know.

Pitfalls.

• Treating an opacity check as a PM test. They measure different things, as our explainer on smoke opacity versus particulate mass sets out.
• Accepting reports without instrument calibration evidence. Ask for the records described in our post on RECD test instrument calibration.
• Not disclosing failures and their corrective actions. A failed test followed by a documented fix and a retest is a credible story; a silently omitted failure is a restatement waiting to happen.

Verified PM reduction percentage from certified tests

Definition. The particulate matter capture efficiency of the RECD, as demonstrated by type-approval testing and, where available, by your own before-and-after site tests carried out by an accredited laboratory.

Data sources. The type-approval certificate and test report (CPCB’s procedure requires at least 70% PM capture for type approval), plus site test reports with upstream and downstream sampling under matched load.

Formula. Reduction % = (PM upstream − PM downstream) ÷ PM upstream × 100, computed on the same basis (same units, same load, same correction). Our walkthrough on calculating RECD particulate reduction covers the detail, and our guide to reading an RECD test certificate explains what the certificate does and does not prove.

Pitfalls.

• Quoting a brochure’s “up to” figure as your fleet’s achieved result. Report the tested figure for your sets, or the type-approval minimum, and say which.
• Comparing upstream and downstream samples taken at different loads or with dilution differences. Our post on how dilution misleads before-and-after measurements shows how big that error can be.
• Averaging percentages across sets of very different sizes. A simple average of a 125 kVA set and a 625 kVA set overweights the small one; weight by baseline PM mass if you need a fleet figure.

Tier 2 metrics: report with method notes

Tier 2 metrics are useful and often requested, but each one embeds at least one assumption. The rule is simple: if you publish the number, publish the method beside it.

Estimated PM mass avoided (kg per year)

Definition. The estimated mass of particulate matter that would have been emitted by the fitted sets without the RECD, minus what was emitted with it.

Formula.

PM avoided (kg) = baseline emission factor (g/kWh) × energy generated on fitted sets (kWh) × verified reduction (%) ÷ 1,000

If you do not have metered kWh, you can substitute run-hours multiplied by an average load in kW, but that adds another assumption and must be stated.

Where the baseline factor should come from. Ideally, from your own upstream test results expressed in g/kWh. Many Indian stack test reports give concentrations in mg/Nm3, which cannot be multiplied by kWh directly. Converting needs the exhaust flow and the engine power at the time of the test. Our explainer on mg/Nm3 versus g/kWh for RECD emissions covers the conversion and its traps. If you must borrow a factor from the engine’s emission certification or a published dataset, say so and explain why it is representative.

Method note should state:

• Source and date of the baseline factor, and the load at which it was measured.
• Source of kWh (meter, controller log, or estimated from hours and load).
• The reduction percentage used and whether it is the type-approval minimum or a site-tested figure.
• That the result is an estimate, with a sensible range.

PM emission intensity

Definition. Estimated PM emitted per unit of DG electricity generated, in g/kWh, across the whole DG fleet (fitted and unfitted).

Formula. Total estimated PM emitted (g) ÷ total DG kWh generated.

This emission intensity metric normalises for how much the generators ran: a year of heavy grid outages raises total PM even if every set is fitted, while intensity shows whether the fleet itself got cleaner. It inherits every assumption in the PM mass estimate.

Maintenance and availability KPIs

RECDs need routine attention, and maintenance data shows whether the device is likely to have performed as tested throughout the year. Useful KPIs include:

• Scheduled RECD services completed ÷ scheduled, per the supplier’s maintenance plan.
• Hours a fitted DG ran with the RECD in an alarm or fault state, where your design logs this, as a percentage of fitted run-hours.
• Mean time to restore after an RECD fault.
• Back-pressure readings within the supplier’s stated range, where a sensor or manual gauge exists.

They sit in Tier 2 because definitions vary between sites and suppliers. Our RECD maintenance guide lists the routine checks that generate this data.

Tier 3 metrics: avoid or caveat heavily

Tier 3 is where most greenwashing risk lives. None of these topics is forbidden, but each requires conversions or factors that a company cannot measure itself, or claims an effect the device does not deliver.

Black carbon and climate-equivalent figures

Diesel soot is largely black carbon, and black carbon has a warming effect. It is tempting to convert “kg PM avoided” into “tonnes CO2-equivalent avoided”. Doing so requires an assumed BC fraction of PM, a global warming potential for black carbon and a chosen time horizon, all of which vary widely in the literature. Your RECD tests measure PM mass, not black carbon, and the CPCB procedure has no BC requirement at the time of writing. Filter capture also differs by design and particle type, as DieselNet’s overview of diesel particulate filters shows. Our analysis of the black carbon particulate reduction claim explains the gap. If you mention black carbon, do it qualitatively and keep it far away from your GHG totals.

“Pollution prevented” and health claims

Statements such as “prevented X hospital admissions” depend on dispersion, background concentrations, population exposure and concentration-response functions that a company with six generators cannot supply. You can say, accurately, that diesel particulate is harmful and that reducing it at source is a recognised control. Do not attach a quantified health outcome to your RECD programme.

CO2 reductions

An RECD does not reduce CO2. Any line that implies it does will fail scrutiny. Refer to the CO2 analysis linked earlier and report Scope 1 from fuel.

NOx reductions

A particulate filter or oxidation catalyst does not meaningfully reduce total NOx. Catalysed designs can shift part of the NO to NO2, but total NOx is essentially unchanged; real NOx reduction needs technologies such as SCR. Our post asking whether RECDs reduce NOx covers the chemistry. In your BRSR NOx row, report whatever your stack tests show, but do not attribute any change to the RECD unless a properly designed test demonstrates it.

Worked example: six DG sets, one reporting year (illustrative)

All figures in this example are illustrative and invented to show the arithmetic. They are not test results for any product or site.

A listed manufacturer has six DG sets in scope. Four have CPCB type-approved RECDs that were commissioned before the start of the year; two do not.

Set	Rating (kVA)	RECD fitted?	Run-hours	Metered kWh
A	625	Yes	450	1,35,000
B	625	Yes	300	90,000
C	500	Yes	500	1,25,000
D	320	No	600	90,000
E	250	Yes	800	1,00,000
F	125	No	150	9,000
Total	2,445	4 of 6	2,800	5,49,000

Sanity check: Set A averaged 1,35,000 ÷ 450 = 300 kW, about 60% of a 625 kVA set’s roughly 500 kW rating at 0.8 power factor.

Step 1: coverage three ways

• By count: 4 ÷ 6 × 100 = 66.7%
• By capacity: fitted kVA = 625 + 625 + 500 + 250 = 2,000. Coverage = 2,000 ÷ 2,445 × 100 = 81.8%
• By run-hours: fitted hours = 450 + 300 + 500 + 800 = 2,050. Coverage = 2,050 ÷ 2,800 × 100 = 73.2%
• By energy: fitted kWh = 1,35,000 + 90,000 + 1,25,000 + 1,00,000 = 4,50,000. Coverage = 4,50,000 ÷ 5,49,000 × 100 = 82.0%

The capacity figure (81.8%) flatters the programme, because unfitted Set D is one of the hardest-working sets. Run-hour coverage (73.2%) is the more honest air-quality picture and points to the next retrofit priority.

Step 2: estimated PM avoided

Assume the company’s own upstream tests, converted from mg/Nm3 to g/kWh using measured exhaust flow and engine output, give a representative baseline of 0.2 g/kWh (illustrative). Assume site tests on the fitted sets demonstrated an average 80% PM reduction (illustrative, weighted by baseline PM mass).

• Baseline PM from fitted sets without RECD: 0.2 g/kWh × 4,50,000 kWh = 90,000 g = 90 kg
• PM avoided: 90 kg × 80% = 72 kg
• PM actually emitted by fitted sets: 90 − 72 = 18 kg

Step 3: fleet PM emitted and intensity

• PM from unfitted sets D and F: 0.2 g/kWh × (90,000 + 9,000) kWh = 0.2 × 99,000 = 19,800 g = 19.8 kg
• Total estimated PM emitted: 18 + 19.8 = 37.8 kg
• Fleet PM intensity: 37,800 g ÷ 5,49,000 kWh = 0.069 g/kWh (rounded from 0.0689)

Without any RECDs, the same generation would have emitted 0.2 × 5,49,000 = 1,09,800 g, or 109.8 kg. Check: 109.8 − 72 = 37.8 kg, which matches.

Step 4: show the uncertainty

The baseline factor is the weakest input. If the true baseline lay anywhere between 0.1 and 0.3 g/kWh (illustrative range), PM avoided on fitted sets would be:

• 0.1 × 4,50,000 = 45,000 g = 45 kg; × 80% = 36 kg
• 0.3 × 4,50,000 = 1,35,000 g = 135 kg; × 80% = 108 kg

So a fair disclosure says “an estimated 72 kg (range roughly 36–108 kg)” rather than “72 kg” alone. In this example the coverage figures are Tier 1; the 72 kg and 0.069 g/kWh are Tier 2 and travel with their method note.

ESG data quality for emission control: building the evidence trail

Assurance providers test whether a number can be traced, recalculated and explained. Assemble the evidence before the deadline, not after the assurer’s query list arrives.

What the evidence trail should contain

Metric	Primary evidence	Supporting evidence
Coverage by count/kVA	Asset register, commissioning reports	Type-approval certificates matched to engine ratings, site photos with serial numbers
Coverage by run-hours/kWh	Hour meter or controller exports, energy meter readings	Monthly DG log sheets, opening and closing readings signed off
Compliance pass rate	Laboratory test reports	Sampling plan, consent conditions, calibration certificates, lab accreditation
PM reduction %	Type-approval report, site upstream/downstream tests	Load records during tests, test witness notes
PM avoided / intensity	Calculation workbook with locked formulas	Method note, source of baseline factor, reviewer sign-off
Maintenance KPIs	Service reports, work orders	Supplier maintenance schedule, alarm logs where available

If you use an accredited laboratory, keep a copy of its scope of accreditation on file and check that it covers stack emission sampling.

Estimation disclosures

When any figure is estimated, say so in the report itself, with a short note on method, assumptions and data gaps. If some sets lacked hour meters for part of the year, disclose how missing hours were estimated (for example, from fuel issue records) and what share of total hours this represents.

Restatements

Errors happen: a set counted as fitted that was commissioned after year end, or a baseline factor from the wrong engine model. Correct them openly, stating the original figure, the corrected figure, the reason and whether prior-year comparatives were restated. An agreed materiality threshold for restatement beats ad-hoc decisions under deadline pressure.

Assurance-readiness checklist

• Reporting boundary defined: which entities, sites and DG sets are in scope, and why any are excluded.
• Every fitted set linked to a type-approval certificate that covers its engine rating.
• Commissioning dates recorded, so part-year coverage can be calculated if a set was fitted mid-year.
• Hour and energy readings captured at period start and end, with signatures.
• Test reports from accredited laboratories, with calibration evidence and load conditions.
• Calculation workbook version-controlled, with formulas visible and a reviewer named.
• Method notes drafted for every Tier 2 metric.
• Tier 3 statements reviewed by someone outside the project team for overclaiming.
• Prior-year figures recalculated on the current method, or the difference explained.

If you run an environmental management system, these records overlap with what your auditors already expect, which keeps RECD ESG reporting cheap to maintain. Our sibling post on including an RECD project in an ISO 14001 environmental programme shows how to make the same records serve both purposes. The environmental compliance checklist for generator owners is a useful cross-check for the compliance documents.

Sustainability report wording for DG generators: good versus misleading

The same project can be described accurately or misleadingly with only a few words of difference.

Misleading statement	Better statement	Why
“Our generators are now pollution-free.”	“RECDs are fitted on four of six DG sets, covering 73% of DG run-hours in FY 2025-26.”	No combustion source is pollution-free; coverage is factual and traceable.
“RECDs reduce emissions by up to 96%.”	“Site tests by an accredited laboratory showed PM reductions averaging 80% on fitted sets.”	“Up to” is a best case for a product; your tested result is your evidence.
“We avoided 72 tonnes of pollution.”	“We estimate 72 kg of PM was avoided (range about 36–108 kg); method in note X.”	Correct units, correct pollutant, range and method stated.
“RECD installation cut our carbon footprint.”	“Scope 1 emissions from DG sets are calculated from diesel consumed; RECDs control particulate, not CO2.”	An RECD does not reduce CO2.
“Emissions of NOx were reduced through RECDs.”	“NOx is reported from stack tests; RECDs are not a NOx control technology.”	Total NOx is essentially unchanged by filters and oxidation catalysts.
“All DG sets are fully compliant.”	“All seven required stack tests were conducted and passed; one test scheduled for Q4 was delayed and completed in Q1.”	Shows the denominator and discloses the exception.

A related pitfall is implying that the RECD earned an external rating. Fitting an RECD can contribute evidence to a green building assessment or an ESG questionnaire, but it never guarantees a credit or score. Our sibling post on whether RECD installation can support a green building assessment explains where that evidence fits and where it does not.

Engineering teams sometimes worry that ESG reporting will expose weak spots. It will, and that is useful: a low run-hour coverage figure is a business case for the next retrofit. Agree the metric menu with the CFO office and assurer at the start of the year, and run the calculations once mid-year to find gaps while they can still be fixed.

When you receive supplier case studies or reference data to support your figures, treat them as you would any third-party claim. Our sibling post on which results in an RECD case study a buyer should trust offers a reading method that applies equally to ESG evidence.

FAQ

Should RECD outcomes go in the GHG section of BRSR?

No. RECDs control particulate matter, which belongs with air emissions other than GHG and in the narrative on air pollution control. Scope 1 CO2 from DG sets is calculated from fuel consumed and is unaffected by the RECD.

What is the single most reliable RECD metric to disclose?

Coverage weighted by run-hours or kWh. It is directly counted from meters and asset records, is easy to assure and reflects actual exposure better than coverage by number of sets.

Can we use the brochure’s PM reduction figure in our report?

Only if clearly labelled as the supplier’s stated or type-approval figure. It is better to report the result from accredited site tests on your own sets, or the type-approval minimum of 70%, and say which you used.

How should we report PM in BRSR when the unit is not prescribed?

Choose a mass unit (kg or tonnes per year) for the annual figure, state it explicitly, keep it consistent year on year and explain the estimation method. If you also report concentrations in mg/Nm3, label them separately so readers do not add them together.

Is it acceptable to estimate PM avoided if we have no baseline tests?

It is possible, but the result is weaker. Use a documented factor from a credible source, explain why it represents your engines, show a range, and plan baseline testing for the next cycle.

Do RECDs improve our ESG rating?

Not automatically. Ratings and questionnaires vary in what they reward. A well-evidenced RECD programme can support your air-quality disclosures, but no device guarantees a score or credit.

Need Evidence You Can Put in a Report?

Credible RECD ESG reporting starts with properly documented equipment. Aceget supplies CPCB type-approved retrofit emission control devices for DG sets from 25 kVA to 2500 kVA, and our product page describes a silicon carbide filter with a precious-metal coating and an oxidation stage, with particulate reduction of up to about 96% depending on DG condition and fuel. For reporting, though, we recommend relying on your own tested results. You can review our type-approval documents on the certifications page, and if you need help assembling commissioning records, test reports or set-wise data for your disclosure, contact our team.

Related Reading

• Including an RECD project in an ISO 14001 environmental programme
• Can RECD installation support a green building assessment?
• Reading an RECD case study: which results should a buyer trust?
• Does an RECD reduce CO2 emissions?
• RECD emissions in mg/Nm3 versus g/kWh
• How to calculate RECD particulate reduction