Carbon Reduction Planning and Scenario Modelling for Australian Businesses

Sixty-six percent of ASX200 companies have made net zero commitments. Only 13% have what EY calls a "credible, actionable transition plan." And when the Investor Group on Climate Change tested twelve major ASX-listed companies in high-emitting sectors against their capital allocation framework, exactly one met the high-alignment threshold for more than half the criteria.

One out of twelve.

That gap between announcement and action is where carbon reduction planning and scenario modelling comes in. Not the aspirational kind — where you put "net zero by 2050" on slide 14 of an investor deck — but the operational kind. The kind that says: "In FY2028, we replace four gas boilers across two sites for $720K total, removing 1,360 tonnes of Scope 1, with a blended payback of 4.6 years assuming gas prices hold above $18/GJ."

We built Carbonly's carbon planning module because we kept seeing the same problem. Companies had a target. They had emissions data (sometimes). What they didn't have was anything connecting the two — a year-by-year model of which actions get taken, in what order, at what cost, producing what reduction. Without that, a net-zero target isn't a plan. It's a press release.

The difference between a target and a plan

A target is a destination. A plan is a route. And a scenario model is what happens when you test whether the route actually works under different conditions.

AASB S2 paragraph 14(a)(iv) requires disclosure of "any climate-related transition plan the entity has, including information about key assumptions used in developing its transition plan, and dependencies on which the entity's transition plan relies." Paragraph 14(b) adds a resourcing requirement — you need to explain how you're funding and resourcing activities. And from your second reporting period, paragraph 14(c) requires quantitative progress reporting against previously disclosed plans.

That's not a vague ask. That's: show your working.

The Australian Treasury released its draft climate-related transition planning guidance in August 2025, aligned to the IFRS TPT Disclosure Framework. The message is clear — "we intend to invest in decarbonisation" isn't sufficient. Credible plans need specific actions, timelines, capital allocation, and interim milestones. And they need to demonstrate that you've stress-tested them under different scenarios.

But here's what that actually looks like in practice, because the regulatory language doesn't help much when you're sitting in front of a blank spreadsheet wondering where to start.

Start with your measured baseline, not someone else's benchmarks

The most common mistake in carbon reduction planning is starting from industry benchmarks instead of your own data. We see it constantly. A property manager uses "average commercial office" emission intensities from NABERS to set a reduction target, then discovers their actual portfolio runs 40% higher because half the buildings are in Victoria (where the grid emission factor is 0.78 kg CO2-e/kWh) and the other half have gas-fired heating that nobody counted properly.

Your plan has to start from your measured emissions. Not estimated. Not benchmarked. Measured.

That means pulling actual kWh, GJ, litres, and tonnes from utility bills, fuel cards, and waste records — broken down by source, by site, by scope. This is the baseline your plan runs against. It's also what auditors will check first when they review your transition plan disclosures.

In Carbonly, the carbon planning module links directly to your measured emissions data. Your baseline isn't a number you type in. It's calculated from the same bills and records your emissions tracking already processes. Change the data, the baseline updates. Add a new site, it shows up. That connection between plan and measurement is the whole point — without it, you're planning against fiction.

Building the action library: what you'll actually do

Once you've got a baseline, you need a library of reduction actions. Not a wish list. A structured set of initiatives, each with an estimated abatement potential, capital cost, operating cost change, implementation timeline, and dependencies.

Here's where most plans go wrong. They list actions in isolation. "Install rooftop solar." "Electrify fleet." "Switch to renewable energy PPA." But actions have dependencies. You can't electrify your forklift fleet before you've upgraded the switchboard. You can't claim market-based Scope 2 reductions from a PPA before the contract structure and LGC retirement method are sorted. You can't replace gas boilers with heat pumps at a food processing facility without confirming the heat pump can deliver the process temperatures you need.

Carbonly's planning module handles this with dependency mapping across eleven action categories: energy efficiency, renewable energy, process optimisation, fuel switching, electrification, waste reduction, supply chain engagement, carbon capture, behaviour change, offsetting, and a catch-all "other." Each action gets a financial profile — ROI, payback period, and NPV auto-calculated — so you're not just modelling carbon, you're modelling cost. Because that's what the CFO asks about first.

Consider a mid-size manufacturer with 8,200 tonnes CO2-e baseline. Their action library might look something like this:

LED lighting upgrade across three sites: $85K capex, 120 tonnes/yr reduction, 2.1-year payback
100kW rooftop solar at main facility: $140K capex, 195 tonnes/yr reduction (at NSW 0.64 factor), 3.5-year payback
Replace two gas boilers with heat pumps: $340K capex, 680 tonnes/yr Scope 1 reduction, 5.8-year payback (depends on gas price trajectory)
Fleet transition — 8 diesel utes to BEV: $280K net capex after FBT exemption savings, 145 tonnes/yr, 6.2-year payback
Renewable energy PPA: $0 capex, ~2,800 tonnes/yr market-based Scope 2 reduction, but location-based stays the same

That adds up to roughly 3,940 tonnes of identified reductions — about 48% of baseline. Nowhere near net zero. Which is exactly the point. The plan shows what's achievable, what it costs, and where the gap is. The gap is what you then have to be honest about in your AASB S2 disclosures.

Scenario modelling: stress-testing your plan

A single reduction pathway is a guess. Multiple scenarios are a strategy.

AASB S2 requires scenario analysis using at least two temperature pathways — one aligned with 1.5 degrees Celsius and one exceeding 2 degrees. Your carbon reduction plan should feed directly into that analysis. Under a high-ambition pathway, your plan might assume aggressive electrification, rising ACCU prices pushing early action, and favourable policy settings. Under a business-as-usual pathway, you might defer the more expensive actions and lean heavier on offsets.

Carbonly's scenario engine runs nine scenario types: baseline, optimistic, pessimistic, realistic, BAU, planned, ambitious, target-driven, and custom. Each takes the same action library but applies different assumptions about implementation timing, cost escalation, policy changes, and carbon price trajectory.

The practical value shows up in conversations with the board. Instead of presenting one trajectory and hoping nobody asks "what if," you present three or four. "Here's what happens if we execute everything on schedule. Here's what happens if we defer the fleet transition by two years because of supply constraints. Here's what happens if ACCU prices hit $70 by 2030 instead of staying at $35."

For Safeguard Mechanism facilities, this matters even more. Baselines decline at 4.9% per year to 2030. If your scenario model shows you exceeding your baseline in 2028 under the pessimistic case, you can quantify the cost — at current market rates of $35-40 per ACCU, a 10,000-tonne exceedance costs $350K-$400K. At the cost containment price of $82.68, it's over $826K. That's the kind of number that gets capex approved for the heat pump project you've been deferring.

Year-by-year trajectory modelling gives you three lines on a chart: baseline (flat or BAU growth), target (linear interpolation between now and your target year), and projected (cumulative effect of your planned actions). The gap between projected and target is your honest admission of how much work remains. Interim milestones — FY2028, FY2030, FY2035 — let you track whether you're on pace or drifting.

What the model can't do (and you shouldn't pretend it can)

We're honest about the limitations, because overstating what scenario modelling delivers is its own form of greenwashing.

Accuracy degrades beyond five to seven years. Technology costs change. Regulations shift. Grid emission factors decline as renewables displace coal (SA's factor dropped from 0.45 to 0.22 over a decade). Any projection beyond 2032 or so should be treated as directional, not precise. We let you model out to 2050 because SBTi and AASB S2 require long-term targets — but the near-term actions in the next three to five years are where the real planning value sits.

Monte Carlo is only as good as your input distributions. Carbonly supports Monte Carlo forecasting alongside linear, exponential, regression, and hybrid methods. Monte Carlo gives you probability-weighted outcomes — useful for understanding the range of possible trajectories. But it doesn't create certainty. If you feed it optimistic assumptions about solar installation timelines or gas price trajectories, you'll get optimistic outputs. Garbage in, probability-weighted garbage out.

The system doesn't know your capex budget. We can calculate that replacing all gas heating across your portfolio costs $2.1 million and saves 3,400 tonnes per year. We can't tell you whether that $2.1 million is available, whether it competes with a warehouse expansion, or whether your board will approve it. The financial modelling — ROI, NPV, payback — helps you make the business case. It doesn't make the decision.

Offset price assumptions can be wildly wrong. EY's January 2026 Australian Carbon Market Outlook projects ACCU prices staying flat at $30-35 through 2028, then rising to around $70 by 2035. But nobody predicted the 2022-2023 price spike to $57, and nobody predicted the subsequent crash back to the mid-$30s. If your plan's viability depends on offsets staying cheap, that's a risk your scenario model should explicitly flag — not hide.

Scope 3 reduction planning is still rough. We can model Scope 1 and 2 reductions with reasonable confidence because you control those sources. Scope 3 depends on your suppliers, your customers, and factors you can influence but not dictate. We include Scope 3 in the planning module, but we won't pretend the precision is comparable.

The offset question: plan for reduction, not purchase

Here's where we take a position that not everyone agrees with.

A credible carbon reduction plan should treat offsets as a last resort for genuinely residual emissions — the 5-10% that can't be eliminated through operational changes. Not as the primary mechanism. The SBTi Corporate Net-Zero Standard requires at least 90% absolute reduction before you can use removals for the remainder. AASB S2 paragraphs 33-36 require you to disclose your planned use of carbon credits separately from your gross target, which means investors can see exactly how much of your "plan" is actually just buying offsets.

We've designed Carbonly's planning module to reflect this. Offsetting is one of eleven action categories — it sits alongside energy efficiency, electrification, fuel switching, and the rest. The system calculates your gross reduction trajectory separately from your net trajectory. If 60% of your planned reduction in 2030 comes from ACCU purchases, that's visible on the chart. And it's probably not going to satisfy your auditors or your internal carbon pricing framework.

The public action library sharing feature exists precisely for this reason. When one organisation models and validates a reduction action — say, switching refrigerant from R-404A to R-290 across cold storage facilities — that action template (with its cost assumptions, abatement potential, and implementation timeline) can be shared across the platform. So the next company doesn't start from zero. Real reduction actions get reused. Offset-heavy plans don't have a template to copy.

The plan workflow: from draft to auditor

A carbon reduction plan isn't a one-shot document. It's a living thing that moves through stages — and the governance around those stages matters for AASB S2 compliance.

In Carbonly, plans move through a defined workflow: draft, in review, approved, active, completed, archived. That workflow creates an audit trail. Your board approved this plan on this date, with these assumptions. You updated it in FY2028 because gas prices changed. You hit your interim milestone for Scope 2 but missed Scope 1 because the heat pump supplier delayed delivery by six months. All of that is documented.

This matters more than most people realise. When AASB S2 paragraph 14(c) kicks in from your second reporting period, you need to show quantitative progress against previously disclosed plans. If your plan lives in a PowerPoint on someone's laptop, that comparison is painful. If it's tracked in a system with version history and milestone checkpoints, it's automatic.

Group 2 entities start reporting from financial years beginning 1 July 2026. That means your first transition plan disclosures appear in your FY2027 annual report. Your second report — the one where progress tracking becomes mandatory — lands in FY2028. You've got roughly 18 months before you need to show that the plan you disclosed is actually being executed. That's not a lot of time to build the system from scratch.

Where to start

Don't try to model everything at once. Start with your two or three largest emission sources — usually electricity (Scope 2) and gas or diesel (Scope 1). Build out the action library for just those sources. Run a realistic scenario and a pessimistic one. See what the five-year trajectory looks like.

Then expand. Add fleet. Add refrigerants. Start the uncomfortable Scope 3 conversations with your top twenty suppliers.

The companies that will handle mandatory reporting most smoothly aren't the ones with the most ambitious targets. They're the ones with the most honest plans — with real numbers, real costs, real timelines, and real admissions about what they don't yet know how to solve.

That's what your auditors want to see. That's what your investors are looking for. And frankly, that's the only way any of this actually results in lower emissions.

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