Chooose · Fuel Trader & Mass Balance

1. SAF Industry Overview

Sustainable Aviation Fuel (SAF) is any aviation fuel that meets certified sustainability criteria — typically a lifecycle GHG reduction of at least 50–65% vs. conventional jet fuel. The market is transitioning from a single-fuel commodity world (one price, no data needed) to a multi-fuel world where every batch carries a sustainability identity with compliance obligations and financial value attached.

1.1 The Value Chain

Five actors connect feedstock to corporate buyer. Each handover transfers physical fuel plus a Sustainability Declaration (SD) — the batch's certificate of authenticity.

Actor	Role	Examples
Feedstock suppliers	Source of raw material: used cooking oil (UCO), animal fat/tallow, agricultural residues, algae, forestry waste. UCO dominates today.	Waste collectors, farms
Refiner / Producer	Converts feedstock into SAF via the HEFA pathway. Gets ISCC or RSB certified. Issues a Sustainability Declaration per batch transferred.	Neste, Phillips 66, Valero, Repsol
Trader ← mass balance tool lives here	Takes legal title to certified SAF and re-issues sustainability claims to customers. Maintains a mass balance ledger. Does not physically process fuel.	Shell Trading, BP, Vitol
Airlines	Burns the fuel (their Scope 1 emissions). Must comply with CORSIA and EU ETS. Also sells SAF credits to corporate buyers (Book & Claim).	AFKLM, BA, Delta, Cathay, Alaska, Southwest, Finnair
Corporate buyers	Decarbonise their Scope 3 value-chain emissions. Buy the sustainability certificate, not the physical fuel. Driven by CDP, SBTi, ESG reporting.	Freight companies, travel managers, shippers

Book & Claim SAF is blended with conventional jet at the airport in a regular tank — you cannot tell it apart physically. The sustainability attributes travel as a separate certificate. A corporate can buy the sustainability credit of SAF burned on a completely different flight. This is auditable because the ledger tracks every credit and debit with an immutable chain of documents.

Scope 1 vs Scope 3 CORSIA and EU ETS are Scope 1 compliance obligations — the airline is directly responsible for emissions from fuel they burn. Corporates address Scope 3 (the airline burned fuel on their behalf) by purchasing SAF credits through Book & Claim.

1.2 Why Software is Needed Now

The current state of the art at fuel desks: Word documents converted to PDFs sent over email. Every producer uses a different PDF layout for Sustainability Declarations — same required fields, completely different format.

Old world	New world
Single fuel type (conventional jet)	Multiple fuel types (SAF + conventional + blends)
Commodity pricing — averages are fine	Bespoke per-batch pricing with sustainability premium
No sustainability data needed per batch	Every batch has a sustainability identity with compliance obligations and financial value
One set of books	Multi-scheme compliance in parallel (ISCC EU + PLUS + CORSIA)

Nobody has built the software rails for this yet. That is exactly what Chooose is building.

1.3 Industry Learning Map

The diagram below maps the complete SAF ecosystem: value chain actors, certification schemes, regulatory drivers, the Chooose platform, and the mass balance tool mechanics.

Figure 1 — SAF Industry · Chooose · Mass Balance Tool — Full Learning Map

2. The Fuel Trader's Job

A fuel trader sits in the midstream of the value chain. In ISCC terminology this is the "Trader" or "Trader with Storage" scope — a party that takes title to certified fuel and re-issues sustainability claims downstream. Critically: they rarely touch the fuel physically. They trade title and documentation.

2.1 The Three Ps

Position Management

The trader holds a "book" — a net position of how much fuel (by volume, energy content, or carbon credits) they own at any given moment, across multiple locations, grades, and certification schemes. Going long or short on SAF vs. conventional jet carries cost and compliance risk. The mass balance tool is literally a ledger of their position.

Price / Spread Trading

SAF commands a premium over conventional jet (currently ~3–8× the price). The trader captures a spread between what they pay the producer and what they charge the airline. This premium comes from both the physical fuel and the sustainability attribute (the certification claim). These two can be separated — a trader can sell the physical fuel at commodity price and sell the sustainability attribute separately as a book-and-claim instrument.

Compliance Obligation Management

Airlines have blending mandates (ReFuelEU, CORSIA). Traders increasingly help airlines meet these obligations by sourcing the right certified volumes and providing the right documentation. Getting the paperwork wrong means the airline's compliance claim is invalid — so documentation accuracy is existential for both parties.

2.2 Day-to-Day Activities

Activity	What happens
Sourcing / contracting	Contact Neste, Phillips 66 etc. Agree on volume, delivery date, price, and which certification scheme (ISCC EU / ISCC PLUS / CORSIA). Negotiate feedstock and GHG value.
Trade execution	Record the purchase in their system. This is a credit to their mass balance pool.
Allocation	When a buyer orders, decide which pool to draw from — which feedstock, which scheme, which carbon intensity — to match supply to the buyer's compliance need.
Dispatch + documentation	Issue a Proof of Sustainability (PoS) to the buyer — attesting volume, feedstock, CI score, and certification. This debits their pool.
Reconciliation	Ensure credits in ≡ debits out + inventory on hand. Any gap is a compliance failure and potentially fraud. This is the mass balance.
Scheme reporting	File periodic reports (monthly/quarterly) to ISCC, CORSIA bodies, etc. attesting that their books balance.
Hedging	Use futures or swap contracts to hedge price exposure on volumes committed to but not yet priced.

2.3 SAF vs Conventional Fuel Trading

Dimension	Conventional Jet	SAF	Why it matters
Pricing	Commodity (IATA benchmarks)	Bespoke, negotiated, scheme-dependent	Trader must manage multiple price curves
Documentation	Bill of lading, delivery note	PoS + batch certificates + feedstock declarations	Documentation accuracy = compliance validity
Compliance	Minimal	ISCC, CORSIA, RED III, ReFuelEU in parallel	Multi-scheme complexity is the core challenge
Fungibility	Full — all jet is jet	Partial — pooled by sustainability profile	Pool management is a new discipline for fuel desks
Temporal risk	None	Scheme year-end: unsold credits can expire	Period management is a new operational requirement
Counterparty risk	Standard	Scheme audits cascade upstream	One invalid upstream cert invalidates downstream

2.4 The Documentation Nightmare (Why Chooose Exists)

Current state: traders receive PDFs from producers (often scanned, OCR'd, formatted inconsistently) and manually re-key the data to create their own PoS to send downstream. That PoS goes as a PDF. The airline re-keys it. Everyone reconciles manually.

Errors mean: airlines lose compliance credit; traders get scheme suspension; both face regulatory penalties. At scale (hundreds of contracts, multiple schemes, multiple pools) this is completely unmanageable by hand.

Chooose's moat Chooose's OCR + AI pipeline ingests any SD format, extracts the structured data, and populates the ledger automatically. On the airline side this is a proven product. On the trader side — the mass balance tool — this is the product this PM role owns.

2.5 What a PM of This Tool Must Deeply Understand

The pool is the product. Every UX decision flows from: what is in which pool, can it go to a buyer with a given scheme requirement, and does the ledger balance?
Schemes are not interchangeable. A CORSIA debit cannot consume an ISCC EU credit. The tool must enforce this structurally.
The PoS is the product output. If you only build ledger views and not PoS generation, you have built half the tool.
Audit trail is non-negotiable. ISCC auditors review the mass balance ledger. Every credit and debit must be traceable to source documents.
Volume and energy content coexist. Traders think in litres or tonnes; schemes require GJ or MJ/kg. Unit conversions must be precise — energy density varies by feedstock.
The scheme eligibility is set on the profile, not on the claim. The tool must prevent a tallow-backed batch from being dispatched under ISCC EU.

3. The Three Certification Schemes

All three schemes run on the same mass balance engine. Behaviour differs only by a small rules table. The pool is partitioned by sustainability profile — not by scheme. The scheme is stamped at dispatch (debit), not at receipt (credit).

3.1 Sustainability Declarations (SDs)

An SD is issued every time certified fuel changes hands. It is the batch's certificate of authenticity. Required fields (mandated by all three schemes):

Feedstock type and country of origin
GHG intensity in gCO₂eq/MJ (carbon emitted per unit of energy, lifecycle / well-to-wake)
Quantity in tonnes or megajoules
Chain of custody method (mass balance is standard)
Certification number of issuer and expiry date
Which scheme(s) the batch is certified under

The "comically messy PDF" problem Every producer (Neste, Valero, Phillips 66) uses a different PDF layout for their SD. Same required fields, completely different tables and fonts. Chooose's OCR + AI pipeline normalises all of them into structured data — the clean layer on top of industry-wide document chaos.

3.2 Scheme Comparison

Rule	ISCC EU	ISCC PLUS	ISCC CORSIA
Purpose	EU mandate compliance. Satisfies ReFuelEU Aviation blending requirements.	Voluntary corporate sustainability claims. No government mandate.	ICAO's global aviation carbon offset for international flights.
Who needs it	All airlines at EU airports (including US carriers). EU fuel distributors under RED III.	Corporates reducing Scope 3 emissions. Freight, travel managers, ESG reports.	Airlines on international routes. Reduces their CORSIA offset obligation.
Feedstock restriction	Must be waste/residue per EU RED Annex IX. UCO qualifies. Non-residue tallow does not.	Wider range than EU. Tallow qualifies even if not EU RED Annex IX eligible.	CORSIA eligible fuel list — SAF with lifecycle GHG ≥10% reduction vs fossil.
GHG threshold	≥65% reduction vs. 89 gCO₂eq/MJ fossil	≥50% reduction vs. fossil baseline	≥10% reduction vs. 89 gCO₂eq/MJ fossil
Claim document	Proof of Sustainability (PoS)	Sustainability Declaration	Sustainability Declaration (CORSIA Eligible Fuel)
Carryover at period close	Full balance rolls to next period (capped by physical stock)	Full balance rolls — uncapped, no physical constraint	Capped at physical stock on hand. Paper credits above physical inventory are forfeited.
Max period	3 months	3 months (12 for farm-level)	3 months
Negative balance	Not allowed — notify certification body immediately	Not allowed	Not allowed
Double counting	Prohibited	Prohibited — serious violation	Prohibited

3.3 The Double-Counting Rule

This is the central audit risk. A batch certified under both ISCC EU and CORSIA has a single physical quantity. The trader can issue a PoS under ISCC EU to Customer A, and a CORSIA declaration to Customer B — but only if the combined dispatched volumes across both schemes do not exceed the total certified input.

Design implication The mass balance ledger must debit the certified pool once regardless of which scheme label is on the outgoing declaration. A batch of 1,000 t can result in 1,000 t of outgoing claims total — not 1,000 under ISCC EU + 1,000 under CORSIA. The scheme is a label on the debit row, not a separate pool.

Event	Pool balance
Buy 1,000 t dual-certified UCO HEFA (ISCC EU + CORSIA eligible)	1,000 t
Dispatch 400 t under ISCC EU to Customer A	600 t
Dispatch 600 t under CORSIA to airline	0 t
⚠ Attempt to dispatch 100 t more under any scheme → REJECTED (pool = 0)	—

4. Regulatory Drivers

Four mandates create the compliance demand that makes the SAF market grow. Each creates a different type of obligation that the trader's documentation must satisfy.

4.1 The Four Mandates

Regulation	What it requires	Chooose angle
ReFuelEU Aviation EU 2023/2405	EU SAF blending mandate. 2% by 2025, rising to 70% by 2050. Applies to ALL airlines at EU airports — including US carriers. Penalty if the airline can't prove compliance. Proof = ISCC EU certification.	Biggest near-term commercial driver for the trader's book. Every airline flying to Europe needs certified SAF and the PoS to prove it.
CORSIA ICAO Annex 16 Vol IV	Global carbon offset for international flights. Airlines offset emissions growth above their 2019 baseline. SAF use reduces the obligation. US not currently enforcing independently.	Bridges SAF and carbon credit markets. An airline can combine SAF claims and carbon offsets to meet its CORSIA target.
EU ETS	EU cap-and-trade. Airlines must buy carbon allowances for intra-EU flights. SAF reduces allowances needed. May expand to international routes.	Creates a direct financial cost for fossil emissions — strengthening the business case for SAF.
Singapore SAF Levy	Mandatory levy at Changi — airlines pay per passenger unless SAF usage is proven. Hybrid model between mandate and voluntary.	Chooose is working with SAFco to be the operating system for this programme. Signal that other hubs may follow.

4.2 GHG Reference Values

Fuel	gCO₂eq/MJ	Reduction vs fossil	Qualifies for
Fossil jet fuel (baseline)	89	—	—
UCO HEFA SAF (illustrative)	~18.5	~79%	ISCC EU (≥65%), ISCC PLUS (≥50%), CORSIA (≥10%)
Tallow HEFA SAF (illustrative)	~31.0	~65%	ISCC PLUS (≥50%), CORSIA (≥10%) — not ISCC EU (non-residue tallow fails Annex IX)

Important The GHG value is not calculated by the trader — it is inherited from the upstream supplier's certified declaration and copied onto every outgoing PoS unchanged. The tool enforces this by locking ghgValue on the SustainabilityProfile at the point of receipt.

5. Chooose Platform

Chooose is a "middleware" / rails business for the low-carbon fuel market. It does not produce fuel, certify it, or govern the market — it operationalises it. Chooose sits agnostically in the middle of the value chain, connecting producers, traders, airlines, registries, and corporate buyers.

Size	~50 FTE (50% R&D)	Revenue	~$30M ARR
Funding	Series B (~$50M raised)	Market reach	~50% of global commercial aviation on the platform
Investors		Temasek/GenZero, BP Ventures, Shell Ventures, Sound Ventures, Amadeus

5.1 Product 1 — Airline (Established, Scaling)

Manages SAF inventory, Scope 1 reporting (CORSIA, EU ETS), and Scope 3 sales (SAF credits to corporates/freight). Customers: AFKLM, British Airways, Delta, American, Cathay, Alaska, Southwest, Finnair.

Scope 1 reporting — tracks SAF usage against CORSIA and EU ETS compliance obligations
Scope 3 sales — enables airlines to sell SAF credits to corporate buyers (Book & Claim)
Document ingestion — OCR + AI normalises incoming SDs from suppliers of every format
Registry connections — auto-posts certified claims to ISCC, RSB, CORSIA registries

The OCR / AI pipeline — the core moat Neste's SD and Valero's SD contain the same required fields but look completely different as PDFs. Chooose's pipeline ingests any SD format, extracts structured data, and populates the ledger automatically. This is the clean data layer on top of industry-wide document chaos. Status: proven, revenue-generating product.

5.2 Product 2 — Fuel Supplier (Newer — This PM Role)

For traders and producers upstream. Airlines are pulling Chooose upstream to their suppliers — "our airline customers want us on Chooose." Phillips 66 is the first customer; Valero is incoming.

Mass balance ledger for traders — the prototype assignment
Tracks certified inventory across ISCC EU, ISCC PLUS, and CORSIA simultaneously
Issues Proofs of Sustainability (PoS) to downstream buyers
Handles multi-feedstock, multi-scheme complexity per batch

5.3 Strategic Expansion Thinking

Marine / renewable diesel	Need to support mass balance for upstream traders, but not actively pursuing marine as a market yet
Carbon credits	Well-positioned; market not there yet but CORSIA creates the bridge mechanism
Multimodal freight	Natural expansion once airline + fuel supplier products mature
Key tension	"How deep and how wide do you go when" — the ongoing Chooose prioritisation challenge

6. Domain Map & Concepts

The domain map visualises all actors, the certified pool mechanic, the three schemes, chain-of-custody methods, and the GHG unit.

Figure 2 — Actor & Domain Map (mass balance tool ecosystem)

Actor map for fuel-trader mass balance: the platform layer, the physical supply chain, the oversight and registry layer, the certified pool, the three schemes, custody methods, and the gCO2eq/MJ unit An infographic in five bands. Band 1 has three tiers: the Chooose platform on top powering the trader; the physical chain (feedstock, refiner, trader, EU distributor, airline) in the middle; and an oversight layer (certification body, ISCC, Union Database, ICAO/CORSIA) beneath. Band 2 shows one certified pool fed by a 1,000 tonne dual-certified receipt and drawn down by an ISCC EU and a CORSIA claim with a no-double-counting guardrail. Band 3 compares the three schemes. Band 4 lists custody methods. Band 5 compares the fuel's lifecycle emissions to the fossil baseline. trader & platform schemes & claims chain links key rule oversight 1 · the actors — platform, physical chain, and the oversight layer Chooose — the trader's accounting rails Feedstockused cooking oil Refinerprocessing unit Trader — youscope: trader EU distributor Airline oversight & registries — span the whole chain, independent of the physical flow Certification bodyaudits the trader ISCCscheme + registry Union DatabaseEU transaction log ICAO / CORSIAairline reporting ↳ a Sustainability Declaration (the cargo's "passport") travels with every handover 2 · the trader's job — one certified pool, scheme stamped at dispatch received: 1,000 tdual-cert EU + CORSIA certified poolbalance = Σ entries −400 t · ISCC EU PoS −600 t · CORSIA claim guardrail — Σ claims ≤ inputscheme is a label on the way out, not a second pool: the same tonne can't be counted twice. 3 · three schemes, one engine — why each buyer needs one ISCC EUbuyer — EU distributordriver — EU RED targetsclaim — Proof of Sustain.carryover — stock-capped ISCC PLUSbuyer — voluntary buyerdriver — net-zero pledgeclaim — Sust. Declarationcarryover — uncapped CORSIAbuyer — int'l airlinedriver — ICAO offset ruleclaim — CORSIA fuel SDcarryover — stock-capped 4 · chain-of-custody methods — how characteristics move Physical segregationkept physically aparthighest integrity Mass balancemixed in tank,tracked on paper← what we built Controlled blendingfixed certified ratioconstant, known % 5 · the unit — gCO2eq/MJ, lifecycle emissions per unit of energy fossil jet baseline 89 gCO2eq/MJ HEFA SAF (our batch) 18.5 gCO2eq/MJ ↳ ~79% lower than fossil — the emissions reduction the airline reports under CORSIA

6.1 Actor Glossary

Platform Layer

Actor	What it is
Chooose	The SaaS platform the trader runs their accounting and customer data-transfer on. Not in the physical fuel flow — it is the rails.

Physical Chain (Chain of Custody)

Each link is separately ISCC-certified under its own scope. A Sustainability Declaration travels with the fuel at every handover.

Actor	ISCC Scope	Role
Feedstock supplier	Collecting / gathering point	Source of the raw material (e.g. used cooking oil)
Refiner	Processing Unit	Converts feedstock into fuel. Phillips 66 sits here.
Trader	Trader / Trader with Storage	Takes legal title and re-issues sustainability claims. This is who the tool is built for.
EU distributor	Customer	Buys fuel that must count under the EU Renewable Energy Directive.
Airline	Customer	Buys SAF to count against its CORSIA offset obligation.

Oversight & Registry Layer

Actor	Role
Certification body	Independent accredited auditor. Certifies the trader and verifies their mass balance.
ISCC	Scheme owner. Writes the chain-of-custody rules and maintains the public certificate registry.
Union Database (UDB)	EU's central database under RED III. Traders must record renewable-fuel transactions here.
ICAO / CORSIA	UN aviation body and its offset framework. Where airlines report SAF claims.

6.2 Chain-of-Custody Methods

Method	How it works	Status in the tool
Physical segregation	Certified material kept physically apart from non-certified. Highest integrity, least flexible. Not commonly used for SAF at scale.	Named for completeness; not modelled
Mass balance	Certified and non-certified physically mixed, but tracked separately on an accounting basis. Claimed output must not exceed certified input.	✓ What the tool implements
Controlled blending	Blending at a constant, known, verifiable certified ratio. Ratio must be constant and documented. Only for Trader with Storage scope.	Named in data model; not fully modelled

7. Mass Balance Tool Design

The prototype is a Vite + React + TypeScript + Tailwind client-side app (localStorage, deployable via Netlify Drop). Pure framework-agnostic domain core/ tested with Vitest. 10/10 tests green.

7.1 Core Design Principles

1. Append-Only Ledger (Event Sourcing)

Entries are never edited or deleted. Corrections are reversing entries. The current balance is a fold over the event log. This is what makes the books defensible under ISCC audit. In code: book.entries is push-only, never spliced.

2. Pool Partitioned by Sustainability Profile, Not by Scheme

ISCC requires "separate bookkeeping for all materials with different sets of sustainability characteristics." The balance is split by the physical sustainability identity (feedstock, origin, GHG value) — not by which certification scheme it will be claimed under. Two different profiles = two separate pools, never aggregated.

3. Scheme is a Label Applied at Dispatch — Never a Balance

This is the mechanism that makes double-counting structurally impossible. A debit subtracts from the single shared pool and is stamped with the scheme the customer needs. The same tonne cannot be spent twice because the pool only goes down once.

7.2 Data Model

SustainabilityProfile — the pool key

Field	Description
`product_type`	e.g. "HEFA SAF"
`feedstock`	e.g. "Used Cooking Oil"
`country_of_origin`	e.g. "NL"
`ghg_value`	gCO₂eq/MJ — travels with the credit, copied onto outgoing claims. Locked at receipt.
`scheme_eligibility`	set, e.g. {ISCC_EU, CORSIA} — the legal labels allowed at dispatch
`coc_method`	mass_balance \| physical_segregation \| controlled_blending
`waste_residue`	bool — affects credit-transfer rules under EU RED Annex IX

LedgerEntry — append-only source of truth

Field	Description
`entry_type`	credit \| debit \| carryover_in \| carryover_out \| adjustment \| conversion
`quantity_t`	signed (+ credit, − debit)
`scheme_claimed`	only on debits, else null — this is how double-counting is prevented
`source_doc_type`	incoming_sd \| outgoing_claim \| period_close \| correction
`created_at`	immutable — the audit timestamp

7.3 Enforced Invariants

No negative closing balance — any profile, any period, all schemes
Carryover ≤ physical stock (CORSIA and EU); uncapped (ISCC PLUS)
scheme_claimed must be in profile.scheme_eligibility — tallow cannot back an ISCC EU claim
Periods contiguous, ≤3 months, no gaps
Append-only ledger: no UPDATE/DELETE; corrections are reversing entries
Supplier certificate valid at dispatch date

7.4 The Dual-Claim Scenario (Core Demo)

1,000 t UCO HEFA batch — dual-certified for ISCC EU and CORSIA.

Event	Entry type	Quantity	Scheme stamped	Pool balance
Buy from refinery (eligible: ISCC EU + CORSIA)	credit	+1,000 t	—	1,000 t
Dispatch to EU Distributor B.V.	debit	−400 t	ISCC EU	600 t
Dispatch to Sky Atlantic Airways	debit	−600 t	CORSIA	0 t
⚠ Attempt to dispatch 500 t more → MassBalanceError thrown	—	—	—	0 t (blocked)

The naive "ISCC EU account + CORSIA account" model would allow −1,000 under each (a violation). This model cannot represent that because there is only one pool.

8. ISCC Rules Reference

Extracted from ISCC EU System Document, ISCC PLUS Chain of Custody v1.1, and ISCC CORSIA Traceability and CoC v2.0 — copies are in your Chooose folder.

8.1 Period & Carryover Rules

Rule	Detail
Period length	Maximum 3 months for traders. Periods must be continuous — no gaps, even with no movement. Adjustments must be declared to the certification body in advance.
Carryover (ISCC PLUS)	Positive credits can carry over period-to-period regardless of physical stock level. Uncapped.
Carryover (CORSIA / EU)	Positive credits can carry over, but cannot exceed physical stock at end of period. Paper credits above physical inventory are forfeited at close.
Negative balance	Never permitted in any scheme. If it occurs, the certification body must be notified immediately.

Carryover example 200 t closing balance, 50 t physical stock on hand under CORSIA → only 50 t carries forward. The 150 t paper advantage is lost. Reason: CORSIA requires alignment between ledger credits and fuel actually in the tank — it prevents purely financial positions.

8.2 Required Documentation Per Period

Per ISCC PLUS p25 / CORSIA p37, each period must record:

Start and end date of period
Opening inventory (certified and non-certified)
Amount + description of all incoming material (with incoming SD references)
Amount + description of all outgoing material (with outgoing SD references)
Credits carried from previous period (if any)
Credits available to carry to next period
Conversion / consumption factor (if processing occurred)

Scheme rules on double-counting (verbatim)
"Multiple accounting (application of the sustainability characteristics more than once) is not allowed under ISCC. Multiple accounting is a serious violation." — ISCC PLUS p6

"If a company is simultaneously certified under more than one certification scheme, double accounting of certain amounts of sustainable material in the certification schemes used is not allowed." — ISCC CORSIA p33

8.3 Outgoing SD — Required Fields

Field	Required by
Unique SD reference number	All schemes
Date of issuance	All schemes
Issuing party (name + ISCC certificate number)	All schemes
Receiving party	All schemes
Product / fuel type and quantity	All schemes
Country of origin of raw material	All schemes
Feedstock type	All schemes
Certification scheme (ISCC EU / CORSIA / PLUS)	All schemes
Chain of custody method	All schemes
GHG emission values (gCO₂eq/MJ) — default or actual	All schemes
CORSIA Eligible Fuel designation + lifecycle emissions reduction vs fossil baseline	CORSIA only
Both scheme references (on same SD or separate SDs)	Dual-certified batches

8.4 Controlled Blending (Trader with Storage)

If the trader physically blends certified and non-certified fuel:

The ratio of certified to non-certified must be constant, known, and verifiable throughout the process
Key rule: certified% of output ≤ certified% of input
If the ratio drifts, it can no longer be called Controlled Blending
Conversion factors apply: certified output = certified input × conversion_factor

9. Further Reading

9.1 Primary Sources (Regulatory / Scheme Rules)

Source	What to look for
ISCC EU System Document iscc-system.org/certification/iscc-documents/	ISCC-CERT-201 (Mass Balance) and ISCC-CERT-205 (Audit requirements)
ISCC PLUS Chain of Custody v1.1 Same portal	ISCC-PLUS-203-2. Especially p25 (documentation per period), p33–34 (flexibility / credit mass balance), p6 (multiple accounting prohibition)
ISCC EU Mass Balance Guidance v1.2 📁 In your Chooose folder	Detailed operational guidance on period management, carryover, and reporting. Dec 2025.
ISCC CORSIA 203 Traceability and CoC v2.0 📁 In your Chooose folder	Chain-of-custody rules for CORSIA. p33 (double accounting), p37 (documentation), p18–19 (SD required fields)
CORSIA SARP Annex 16 Volume IV icao.int/environmental-protection/CORSIA/	ICAO's scheme rules. Heavy but canonical.
ReFuelEU Aviation Regulation (EU) 2023/2405 eur-lex.europa.eu	The blending mandates your airline customers must comply with
EU RED III (Directive 2023/2413) eur-lex.europa.eu	Sustainability criteria framework underlying ISCC EU. Defines which feedstocks qualify under Annex IX (waste/residue list)

9.2 Accessible Explainers & Podcasts

Source	Why useful
Rocky Mountain Institute	"SAF: A guide for airlines" and "Scaling SAF" reports. Practical, free, well-written.
IATA SAF Hub — iata.org	Tracks global SAF mandates and publishes trader guidance. Good for regulatory updates.
SkyNRG Knowledge Hub	SkyNRG is a major SAF trader. Their published guides are unusually clear on operational mechanics.
Argus Media / OPIS	Industry price reporters. SAF coverage explains how the market works in practice. (Partly paywalled.)
BloombergNEF SAF Outlook	Annual report. Good for market sizing and trend context.
SAF Investor Podcast	Interviews with producers, traders, airlines. Operational texture and market context.
Aviation Weekly "Check 6"	Covers the airline side. Helps understand the buyer's perspective on SAF compliance.
The New Map — Daniel Yergin	Not SAF-specific but gives you the oil trading mental model that SAF trading grew out of.
The King of Oil — Daniel Ammann	Biography of Marc Rich. Vivid picture of how commodity traders think about position and risk.

9.3 Files in Your Chooose Folder

File	Contents
`DESIGN.md`	Core design principles, full data model, enforced invariants, derived views, and scope for the prototype
`iscc_rules_notes.md`	Extracted operative rules from ISCC EU, PLUS, and CORSIA — with prototype implications for each
`mass-balance-tool/docs/DOMAIN.md`	Domain glossary — every actor and concept in the domain map, grouped by band
`mass-balance-tool/docs/industry-overview.svg`	Full industry learning map (embedded in Section 1 of this document)
`mass-balance-tool/docs/domain-map.svg`	Actor & domain map (embedded in Section 6 of this document)
`ISCC-EU-Mass-Balance-Guidance-Document_Version-1.2_Final_22122025.pdf`	Primary source — ISCC EU mass balance guidance, December 2025
`ISCC_CORSIA_203_Traceability_and_Chain-of-Custody_2.0.pdf`	Primary source — CORSIA chain of custody rules
`ISCC_PLUS_203-2_Chain-of-Custody_v1.1.pdf`	Primary source — ISCC PLUS chain of custody rules
`chooose prototype exercise 4.6.26.docx`	The original recruitment exercise brief from Chooose

Chooose · Fuel Trader & Mass BalanceKnowledge Overview

1. SAF Industry Overview

1.1 The Value Chain

1.2 Why Software is Needed Now

1.3 Industry Learning Map

2. The Fuel Trader's Job

2.1 The Three Ps

Position Management

Price / Spread Trading

Compliance Obligation Management

2.2 Day-to-Day Activities

2.3 SAF vs Conventional Fuel Trading

2.4 The Documentation Nightmare (Why Chooose Exists)

2.5 What a PM of This Tool Must Deeply Understand

3. The Three Certification Schemes

3.1 Sustainability Declarations (SDs)

3.2 Scheme Comparison

3.3 The Double-Counting Rule

4. Regulatory Drivers

4.1 The Four Mandates

4.2 GHG Reference Values

5. Chooose Platform

5.1 Product 1 — Airline (Established, Scaling)

5.2 Product 2 — Fuel Supplier (Newer — This PM Role)

5.3 Strategic Expansion Thinking

6. Domain Map & Concepts

6.1 Actor Glossary

Platform Layer

Physical Chain (Chain of Custody)

Oversight & Registry Layer

6.2 Chain-of-Custody Methods

7. Mass Balance Tool Design

7.1 Core Design Principles

1. Append-Only Ledger (Event Sourcing)

2. Pool Partitioned by Sustainability Profile, Not by Scheme

3. Scheme is a Label Applied at Dispatch — Never a Balance

7.2 Data Model

SustainabilityProfile — the pool key

LedgerEntry — append-only source of truth

7.3 Enforced Invariants

7.4 The Dual-Claim Scenario (Core Demo)

8. ISCC Rules Reference

8.1 Period & Carryover Rules

8.2 Required Documentation Per Period

8.3 Outgoing SD — Required Fields

8.4 Controlled Blending (Trader with Storage)

9. Further Reading

9.1 Primary Sources (Regulatory / Scheme Rules)

9.2 Accessible Explainers & Podcasts

9.3 Files in Your Chooose Folder

Chooose · Fuel Trader & Mass Balance
Knowledge Overview