December 2025 Brown Bag Webinar Recap

Overview

How can mass balance chain-of-custody models be applied consistently and transparently in LCA and EPDs?

In our December Brown Bag session, Jason Pierce, Technology Fellow in Global Sustainability at Eastman and Chair of the ACLCA Mass Balance Working Group, introduced the fundamentals of mass balance credit method and its rapidly evolving role in LCA, PCR development, and environmental product declarations.

The mass balance credit method is a chain of custody (CoC) model which has generated both significant interest and controversy for application in LCA and EPD. Mass balance CoC model has been utilized in various industry sectors for decades but is experiencing significant growth via applications related to circular economy. 

There is a lack of guidance for LCA practitioners on how to integrate mass balance credit method CoC with LCA and EPDs. ACLCA is working to fill in the gap with the development of a mass balance chain of custody addendum to their Open PCR standard. The correct implementation of such guidance could better enable and encourage manufacturers to better utilize recycled content and other types of sustainability-focused inputs into integrated production processes.

This talk provided a basic introduction to the chain of custody topic with a focus on mass balance credit method including benefits, challenges, and recent developments. The session will include an update on the progress underway in the ACLCA mass balance working group.

About the Speaker

Jason Pierce has a Master’s Degree in Chemical Engineering from the University of Louisville. His career spans over 30 years in the chemicals, plastics, and specialty materials industries. He is currently a Technology Fellow in the Global Sustainability division of Eastman, where he gained 16 years of hands on and leadership experience in LCA. 

Jason is active in ACLCA where he won the 2023 LCA Corporate Leadership award. He is an ACLCA certified practitioner and reviewer. He also leads the ACLCA chain of custody mass balance working group. As a side project, Jason founded Blue Ridge Sustainability which currently focuses on LCA and PCR critical reviews.

Edited Webinar Transcript (Sectioned with Timestamps)

0:05–1:28 — Opening & Introduction

Tess Konnovitch (EarthShift Global):
Hello everybody. My name is Tess Konnovitch and I'm the Scientific Marketing Manager here at EarthShift Global. Welcome to our December Brown Bag webinar.

Today we are hosting Jason Pierce, and I'm pleased to welcome him. Jason has a master’s degree in chemical engineering from the University of Louisville. His career spans over 30 years in the chemicals, plastics, and specialty materials industries.

He is currently a Technology Fellow in the Global Sustainability division of Eastman, where he has gained 16 years of hands-on and leadership experience in life cycle assessment—or, as we all know it, LCA.

Jason is active in ACLCA, where he won the 2023 LCA Corporate Leadership Award. He is an ACLCA certified practitioner and reviewer, and he also leads the ACLCA chain of custody mass balance working group.

As a side project, Jason founded Blue Ridge Sustainability, which currently focuses on LCA and PCR critical reviews.

So, welcome Jason. And a quick note for our audience here today: thank you all for joining. You can leave all questions in the Q&A section. I'm really excited to read through these at the end, so please again leave them in the Q&A section and we'll read through them at the end of Jason's talk.

And with that, take it away.

Jason Pierce:
Thank you so much, Tess, and I'd like to welcome everybody and thank you for joining this webinar.

Today, we're going to be giving a basic introduction to a chain-of-custody system called mass balance and its developing application in LCA and EPDs.

First of all, I want to thank ACLCA—the American Center for Life Cycle Assessment. The content in this deck was put together through the effort of almost three years of work from a chain of custody mass balance working group in ACLCA, which I co-lead.

Our agenda today: we're going to take a basic look at chain-of-custody models—there are five different ones we're going to review—then go a little bit deeper into the mass balance chain-of-custody model and talk about emerging considerations in its application in the LCA and EPD space. Then we'll shift gears and talk about what ACLCA has been doing related to chain of custody, LCA, and EPD, and we’ll have a little time at the end for Q&A.

1:28–3:39 — Problem Statement & Context

The problem statement here is that there’s a chain-of-custody system called mass balance that’s getting a lot of traction across many different industries and applications. It’s actually been around for over 20 years, but it’s seeing significant growth, particularly around circular economy technologies.

There’s growing interest in applying mass balance chain of custody to LCA and EPD. However, existing standards and guidelines for LCA and EPD are, for the most part, silent about chain-of-custody systems, including mass balance.

So ACLCA saw an opportunity back in 2023 to form a working group and develop some guidance—and we’re still working on that to this day.

3:39–5:42 — Defining Chain of Custody & ISO 22095 Models

Let’s talk about chain-of-custody models first.

Let me first define chain of custody for you. There’s an ISO standard, ISO 22095, which is Chain of custody — General terminology and models. This is the definition of chain of custody in that standard: It's a process by which inputs and outputs and associated information are transferred, monitored, and controlled as they move through each step in a supply chain.

In this graphic, we’re looking at a very simple supply chain—a linear one. In reality, supply chains are very branched and can get highly complicated. But the basic point we’re trying to convey is that there can be information about a material or product—called a specified characteristic—and the chain-of-custody system tracks that specified characteristic as products move through the supply chain.

At the bottom, I list some examples of typical specified characteristics. They might be something like:

• a recycled feedstock

• a biobased feedstock

• sustainable agriculture or forestry practices

• human rights criteria

There’s a variety of different specified characteristics that are possible.

ISO 22095 defines five different chain-of-custody models, starting from identity preserved down through book and claim.

The first two—identity preserved and segregated—have a very high degree of overall physical presence, which I’ll show you with some examples in a few slides so you’ll understand that better. These involve no mixing; the materials that move through the supply chain are kept segregated from other materials at all times.

But controlled blending, mass balance, and book and claim are chain-of-custody models that do allow mixing.

Even though this is shown as a staircase, it doesn’t imply a hierarchy of importance. As we point out on the slide, some of the more flexible chain-of-custody models really can help enable emerging technologies by stimulating commercialization and scale-up. We’ll have examples of that later too.

5:42–11:10 — Identity Preserved, Segregated, Controlled Blending, Mass Balance & Book and Claim

The first and “tightest” chain-of-custody model is called identity preserved. In this case, all the inputs originate from a single specific source, and they’re kept physically segregated throughout the whole supply chain.

At the end of the supply chain, you can trace the product all the way back to its original single source.

I come from the chemical and plastics industry, so I’m going to use some plastics examples as we move through these.

An example of a specified characteristic here would be “post-consumer plastic waste collected in the city of Rotterdam.” At the end of the supply chain, when you make a plastic product from that material, you can say, “Yes, it’s 100% recycled content from post-consumer waste of the city of Rotterdam,” and you can trace it all the way back.

Segregated is a little bit more flexible, in that the inputs can come from multiple sources, but they have identical characteristics. From that point forward, they’re kept segregated throughout the supply chain.

In this case, the specified characteristic might be “post-consumer plastic waste collected from multiple cities in Europe.” At the end of the supply chain, you can make a claim: “100% recycled content from post-consumer waste from Europe.” You can’t trace it back to an individual city, but you can be certain the product is 100% sourced from Europe.

Now we move into the chain-of-custody systems that involve mixing.

The first one here is called controlled blending. In this model, material with a specified characteristic is mixed with material without that characteristic in a known and constant proportion.

Sticking with the plastics analogy, this is very conventional in terms of how people think about recycled content. In the graphical example on the slide, imagine we’re making plastic cups with an extruder. You put in one bag of recycled plastic and three bags of virgin plastic, mix it all together, and make your cups. You can then claim that each of the items contains 25% recycled content from post-consumer waste. Very straightforward.

Mass balance is a little bit different and more flexible. In this case, you’re mixing materials together and the proportion of specified characteristic varies over time. Claims are made on part of the output, and it involves something called attribution, which we’re going to talk about.

There are actually two implementation methods of mass balance:

• the rolling-average percentage method, and

• the credit method.

In the rolling-average method, it’s actually a bit similar to controlled blending, except that the proportion of specified characteristic in the input varies over time. You set a balancing period—typically three months—and take the average over that period.

In the example on the slide, we’re putting in 25% specified characteristic on average over three months and making a claim on the product that it all contains 25% recycled content using rolling-average mass balance.

The credit method of mass balance allows more flexible attribution. You accrue credits based on how much specified characteristic goes into the system as input, and then you can attribute those credits—based on value choices—to the output.

So some portion of the output might have 0% claimed recycled content using mass balance, another part might have 50%, and so on. At the end of the day, the mass balance ensures you can’t claim more output than the amount of specified characteristic you put into the system on the input side.

Book and claim is the final chain-of-custody system defined in ISO 22095. It’s sometimes known as certificate trading. This is a system where the administrative record flow is not connected to the physical flow of materials.

Another way of saying that: you can sell the product separately from the certificate for the attributes. Think of carbon offsets. There are a number of different environmental attribute certificate programs.

In one example on the slide, a company might say: “We support plastic recycling. In 2020, we purchased recycling certificates equivalent to 25% of our primary packaging.”

That’s a book-and-claim type of system.

11:10–18:21 — Mass Balance in Practice: Rolling Average, Credit Method & Cocoa Example

Here are the different systems we reviewed. Identity preserved through controlled blending are very straightforward in LCA practice. Mass balance and book and claim are not so straightforward, and ACLCA’s working group is focusing on this mass balance one—for both rolling-average and credit methods.

So let’s dive a little deeper into mass balance.

Here’s a numerical example for a rolling-average mass balance. We’re still making plastic cups in an extruder.

• In January, we bring in 250 units of recycled input and 50 units of virgin input.

• In February, it’s all virgin input—300 units.

• In March, it’s a 200/100 split between recycled and virgin.

Over that three-month period, we make 900 units of output. The math works out so that on average we can claim 50% recycled content using mass balance.

But it’s important to note: if you look only at February, anything made in February actually has zero physical recycled content. With a rolling-average mass balance, unlike controlled blending, there is no guarantee of physical content in any specific batch of product, because the claim is based on an average over the claim period.

The system boundary can include a process, a site, or be multi-site—so this can be done over multiple sites averaged together as well.

Here’s an example of a credit-based mass balance.

A simple example I like to use to introduce people to the concept is sustainable cocoa. There are various certification systems for sustainable cocoa—Rainforest Alliance, Fairtrade, and others. This is a generic example, but often in cocoa standards you have sustainable forestry or agriculture practices embedded, including biodiversity protection and human rights criteria.

Companies might want to make claims on the chocolate products that come out of that system. In many regions where cocoa is grown, some farms are certified and others are not, and they feed into a central regional collection system at a cocoa mill.

Typically, there’s one silo, and they mix cocoa from certified and non-certified farms. In this example, over some time period:

• 6 tons of certified cocoa come in

• 12 tons of conventional cocoa come in

They’re mixed together and go through the cocoa mill. It’s not economically or operationally practical to keep certified material separate from conventional material, because it comes in at different times and the equipment isn’t set up for that. So it all mixes together.

The cocoa mill has a yield; in this example, coming out we have 15 tons of beans and we can account for 5 tons as certified using mass balance, and 10 tons as not certified.

Then we move further along the supply chain to make chocolate candy. We might have, say:

• 50,000 candy bars with a certified cocoa label, and

• 100,000 with no claim of certified cocoa.

Mass balance is very important here:

• On the supply side, it makes the certification system operationally and economically practical. Without mass balance, all the cocoa would be blended together and farmers investing in certification would not be recognized in the market.

• On the consumer side, people can choose to buy certified bars knowing their purchase supports certified practices all the way back to the farm.

What mass balance does in this case is limit how many certified cocoa chocolate bars can be made based on the amount of certified cocoa bean input in the system. It balances across the entire system, benefiting farmers, producers, cocoa-growing communities, and the environment.

In practice, you have conventional inputs coming into a system and inputs that bear a specified characteristic. Those create credits that go into a credit account. Those credits can then be applied to products coming out of the system at each stage in the supply chain, with conversion factors that account for yield losses based on actual operations.

In this context, the word “credit” refers to mass balance accounting credits—not to any other type of LCA credit.

18:21–24:54 — Mass Balance & Chemical Recycling; Proportional vs Non-Proportional Attribution

Mass balance has been around for at least 20 years in various industries because they all have one thing in common: it’s not practical to keep more sustainable materials physically segregated from conventional materials.

Mass balance is a hot topic right now because it’s new to circular economy technologies such as chemical recycling of plastics and some biobased technologies.

You may have heard of chemical recycling. Most people are more familiar with mechanical recycling, where plastics are collected, sorted, chopped up, washed, remelted into pellets, and reused. Mechanical recycling is efficient, but it has limitations:

• It doesn’t remove certain additives

• It’s hard to restore material to food-contact quality

• Color and some physical properties degrade over time

Chemical recycling, by contrast, breaks plastics down at the chemical level—into molecules or monomers, the building blocks for new polymers. Those monomers can be purified and repolymerized to make very high-quality plastics.

The challenge is that this is typically done by integrating a recycling operation into a very large existing chemical plant.

In a simplified example, you have virgin chemical feedstocks (from crude oil, natural gas, coal) coming into a plant to make monomers and then plastics. With chemical recycling, you bring in plastic waste, sort it, break it down to molecules or monomers, and feed those into the same plant. Once you’ve made a molecule, you can’t tell whether it came from a fossil source or from plastic waste—there’s no analytical test.

Once material goes into the chemical plant, it’s mixed. You have to use a mass balance chain-of-custody system, typically a credit method mass balance, to do the accounting on recycled content.

In this context, mass balance is an accounting system that allows chemical recycling to happen at massive scale by integrating it into existing assets. The mass balance guarantees that the amount of recycled content attributed to products is balanced with the amount actually recycled in the system.

I also want to talk about an important topic: proportional versus non-proportional mass balance.

When you’re doing attribution, you have two general options:

• Proportional attribution

• Non-proportional attribution

In a simplified example, imagine the yellow box on the slide is a chemical plant scaled to process one million tons per year of feedstocks. Let’s say the plant is able to substitute 100,000 tons per year of plastic waste, replacing some fossil inputs.

With proportional mass balance, you might say: “We’ll attribute 10% recycled content to all outputs from this system.”

The problem is that this really limits market adoption. That 100,000 tons per year is a very large recycling plant—one of the largest in the world—but because it’s integrated into a big chemical plant, everything gets labeled as just 10% recycled. That may not carry enough value in the market to make the recycling system economically viable.

With non-proportional attribution, you might say:

• 90% of the output has 0% recycled content,

• 10% of the output has 100% recycled content.

In this case, you’re linking recycling capability with a meaningful level of attribution that can achieve economics in the marketplace and enable circular economy technology to become viable quickly at large scale.

Over time, more incremental changes can happen through mass balance until you eventually reach a point where mass balance isn’t needed.

Non-proportional attribution is very important for generating meaningful products and enabling technologies to scale. It’s a critical link between recycling capability and stimulation of market demand.

There’s a nice quote from a NIST report that captures some of this: mass balance is a tool to incentivize shifts in supply chains to support more sustainable, environmentally beneficial technologies. It’s widely used in a lot of commodity sectors.

Without mass balance, especially in the chemical recycling example, if you had to keep materials segregated to get high levels of recycled content, you’d have to build parallel plants, parallel storage systems, parallel supply chains, and so on—very expensive, high impact, and time-consuming. It’s much more efficient to integrate into existing assets, which is more affordable, lower impact, and faster to implement.

24:54–33:09 — Challenges, Greenwashing, and the Current Landscape

I also want to spend some time on the challenges of mass balance.

Understandable consumer claims are important. When you’re talking about attribution of specified characteristics—rather than strict physical content—there’s potential for greenwashing if this is not properly managed and communicated.

As I said, attribution is different from direct physical content, and there are debates over attribution choices: proportional vs non-proportional, traceability, connectivity, technical feasibility, system boundaries (single-site vs multi-site), and so on.

There are also issues that are unique to LCA practitioners when considering how to integrate mass balance chain-of-custody into LCA or EPDs. There’s a great article by Professor Frank Biermann (and also work by Frischknecht and others) on “message LCA versus analysis LCA” that I highly recommend if you’d like to read more.

We want to make sure there’s no double counting. We have to think about regionalized impacts—especially when we consider attribution across multiple sites. We need to think carefully about allocation, attribution, and methodology approaches for mass balance in LCA, and about the implications for comparative assertions.

On one slide, we show a “map” of the landscape in 2025.

• In the top left, there are various voluntary guidelines and certifications that have been published in recent years:

  • Together for Sustainability (chemical-industry focused)

  • Catena-X (mass balance for product carbon footprinting in automobiles)

  • ISCC carbon footprint certification

  • SCS-15, and others

• Moving to the right, there are emerging regulations. A very important one is the Single-Use Plastics Directive Implementing Act in Europe, which is expected to recognize mass balance credit method as a means of establishing recycled content in single-use plastics.

• In the lower left, there’s gridlock in the EPD space. Eco Platform—an umbrella group for EPD program operators in Europe—has decided that any mass balance chain of custody is currently not allowed in EPDs there, pending development of consensus guidelines. At the same time, the building and construction industry has been advocating for acceptance of mass balance for innovative products.

• On the bottom right, we list several key publications from authors like Peter Hohne, Ullmann, and Frischknecht. There are also criticism papers, for example from NGOs such as ECOS.

We’ve overlaid red, yellow, and green “stoplights” on the slide to indicate where support is strong, where there is caution, and where there is opposition to mass balance in LCA and EPD. It’s a mixed landscape right now.

33:09–40:02 — Relevant ISO Standards & ACLCA Initiative Overview

There are relevant ISO standards in development.

• ISO 13662 is a new standard, Requirements and guidelines for chain-of-custody mass balance. It gives detailed requirements for mass balance.

• ISO 22095, which I mentioned earlier, is general for all chain-of-custody systems and defines mass balance at a high level.

• ISO 14077 (in development) is Requirements and guidelines for application of chain-of-custody approaches in LCA. This is very relevant to what we’re talking about today, and it includes mass balance chain-of-custody. It’s currently in the second working draft stage, so it’s early in the process, with publication targeted for the end of 2027.

• Standards like ISO 14067 for product carbon footprinting are under revision right now, and there are discussions about potential chain-of-custody annexes or clauses in that standard as well.

Shifting gears, I’d like to talk about ACLCA initiatives in this space.

The first three chain-of-custody models—identity preserved through controlled blending—don’t really need guidance for LCA practitioners. They’re straightforward to handle with conventional approaches.

ACLCA is focusing on:

• Rolling-average and credit-method mass balance, and

• Book-and-claim systems, which are partially addressed through renewable energy certificate (REC) guidance.

For example, ISO 14067 for product carbon footprinting allows renewable energy certificates and guarantees of origin to count under certain circumstances. ACLCA has a document, Quantifying Renewable Energy Electricity Instruments in EPDs (published in 2022 and currently under review).

We didn’t have the bandwidth in this working group to take on book and claim broadly, but at least for electricity it’s partially covered by other ACLCA working groups.

We started the Chain of Custody Mass Balance initiative in ACLCA in 2023 and 2024. We’ve done several things so far:

• Completed a literature survey (there’s not a lot out there specifically on mass balance in LCA).

• Put together an educational slide deck (many of the slides I’m using today come from that effort).

• Held LCA Institute workshops and pre-conference workshops.

• Created an issue brief, which I’ll show in a moment.

• Started drafting text to take into future working groups.

The issue brief is publicly available—you can scan the QR code on the slide or simply search “ACLCA issue brief mass balance.”

The most important part of that document is a set of six principles for credibility. After a lot of discussion and debate across a diverse group, we concluded that ACLCA accepts the practice of including mass balance chain of custody in LCAs and EPDs when certain conditions are in place.

Those conditions are captured in six principles that we listed in the issue brief.

We took that document forward into 2025, and now we’re focused on developing more specific guidelines.

You may know that ACLCA has a set of documents called the Open PCR Standard: guidance and recommendations (not requirements) for PCR program operators. We’re now developing an addendum to the ACLCA Open PCR Standard that will give guidance on:

• Mass balance chain of custody

• How to deal with mass balance credit method and rolling-average method when performing LCA modeling

• How that translates into EPDs for different stakeholders—practitioners, policymakers, standards setters, and others

We have 34 members in the group from different sectors, and we’ve been meeting every two weeks since January.

One of the things I’m proud of is our review of existing standards. We looked at six standards—ISO 14040, 14044, 14025, EN 15804, ISO 21930, and others—and searched for challenging clauses. None of these standards explicitly mention mass balance or chain of custody, so we had to interpret them with chain of custody in mind.

We identified 30 clauses across these standards that could be interpreted as relevant to whether mass balance chain of custody does or does not conform.

Interestingly, we had a split in the group. There was no standard clause that everyone agreed mass balance could not conform to. In fact, most of the group felt that existing standards can be conformed to, with proper interpretation.

One example of a challenging clause is in ISO 14040, which says that the LCA approach should “give preference to describing physical systems” and “be based on natural science.”

One viewpoint is that mass balance chain of custody does not conform, because there’s no guarantee of physical presence of the specified characteristic in outputs.

An alternate interpretation is that mass balance can conform, because:

• The goal and scope of an LCA can explicitly include a chain-of-custody system.

• ISO 14040 acknowledges that decisions can also be based on value choices.

• The standards were written without chain of custody in mind, and there are widely accepted methods like economic allocation that are not strictly based on natural science.

• Renewable energy credits and guarantees of origin—typically book-and-claim systems—are already widely accepted in LCA and, in some cases, in EPDs.

We went through all 30 clauses in a similar way, and then took a poll in the group. The majority clearly agreed that conformance to the standards is possible with appropriate guardrails, but not everyone agreed, and there’s more uncertainty around EPD standards such as ISO 14025, ISO 21930, and EN 15804.

We plan to include this analysis as an annex in our written addendum.

40:02–43:25 — Guardrails & Methodology Work

Looking at the breakdown of responses in that poll, the majority of respondents were from industry, with most in support but not everyone. We also had participation from government and consulting. Overall, it shows pretty good support for the position that LCA and EPD can conform to existing standards when mass balance is used with guardrails.

We’ve also seen this in practice: there are LCA studies that include mass balance chain-of-custody, make comparative assertions, and have gone through ISO 14044 critical review by panels—and were found to conform to ISO 14044.

What we’re focusing on now in ACLCA is the development of guardrails.

If you remember the issue brief, we said ACLCA supports mass balance chain of custody in LCA and EPD provided there are appropriate guardrails.

We’re having a lot of debate and discussion about these guardrails. We currently have 13 under development; we’ve reached consensus on 11 of them. Two are still in progress:

• One around multi-site attribution (site-to-site credit transfers)

• Another around the “like-for-like” requirement in ISO 13662

We’re also developing methodology examples—generic model examples showing how you would apply mass balance chain-of-custody and reflect that in product carbon footprints.

On the slide, I highlighted three example guardrails (from the 11 we’ve agreed on):

1. Distinct naming
   We recommend that when mass balance credit method is used in an LCA or EPD, it be clearly named—for example, “Chain-of-custody EPD using mass balance credit method.” That distinguishes it from conventional LCA/EPD and is consistent with how we differentiate other LCA approaches (dynamic LCA, consequential LCA, etc.).

2. Certification
   We believe it’s very important that a mass balance chain-of-custody system be certified according to a recognized standard and verified by a third-party conformity assessment.

3. Reporting with and without attribution
   We recommend reporting results with and without mass balance attribution. This is important for credibility and for understanding how sensitive results are to attribution choices. Those details should be made available to all stakeholders.

We’re continuing to finalize these guardrails, work through challenging topics (like multi-site credit transfers and biogenic carbon considerations), and refine attribution/allocation methodology examples.

Our goal is to work through most guardrails and decisions by the end of this year and start writing the addendum early next year. There will be a public commenting process as part of the ACLCA Open PCR Standard process, typically a 60-day consultation window.

If you’re an ACLCA member, you’ll likely receive a notification when the document is available for review. Even if you’re not a member, we expect the draft to be open for public comment.

My personal goal is to have this document out for public comment around the end of the first quarter next year, and—if all goes well—published sometime later in 2026.

With that, I want to thank the chain of custody working group members over the past three years. We’ve had a lot of good discussions and different viewpoints, which have really helped sharpen the work. I appreciate all the hard work, input, and patience. It finally feels like we’re coming together and moving toward a deliverable.

I also want to thank EarthShift Global very much for inviting me to give this presentation today.

We have plenty of time left for questions, so I’m going to turn it back to Tess, who will be our moderator.

43:25–55:32 — Q&A and Closing

Q1: Is the credit method mass balancing applicable to renewable energy inputs as well—for example, solar versus grid electricity—or do we have a different methodology for fossil versus renewable energy inputs for energy input balancing?
Yeah, great question. With energy, chain-of-custody systems certainly apply, and it depends on the way the energy—whether fossil or renewable—is delivered from the generation site to the user.

In many cases, such as unbundled renewable energy certificates, that would be a book-and-claim chain-of-custody system.

If you have something like a physical power purchase agreement (PPA)—say there’s a solar farm and you’re on the same grid, but you’re directly contracting for that power—that’s more of a mass balance-type system. There is a possibility of physical presence of electrons from the renewable source in what you’re using.

So, yes, chain-of-custody applies to energy products as well, and ISO 14067 explicitly includes provisions for contractual instruments for renewable energy. It doesn’t explicitly differentiate between book-and-claim and mass balance, but in general, chain of custody is relevant for any product—physical materials or energy.

Q2: The question asker assumes polymer companies that are advertising ISCC PLUS certified polymers are using non-proportional attribution. Is this correct in your opinion?
In my experience, yes, that’s generally correct—though I wouldn’t say it’s 100% true in every circumstance. Typically, non-proportional attribution is used most of the time for chemical recycling in these systems.

Q3: How can LCA analysts address the underlying risks of greenwashing associated with misunderstandings of the credit-based mass balance approach?
Yeah, great question—and that’s something we’re wrestling with in our group.

You get into the claims and what a consumer can reasonably understand when you’re talking about mass balance chain-of-custody. There’s a whole field of work exploring this right now.

I think transparency is critical. One of the things I mentioned was distinguishing that this is a chain-of-custody LCA, not just a conventional LCA.

I also believe it’s the LCA practitioner’s responsibility to monitor and feel confident in the claims related to the LCA. Anything we can do around transparency and following clear, transparent guidelines is really important.

It’s a little bit of the “wild west” right now, and that’s part of why we want to develop guidance in ACLCA, and why ISO 14077 is in development. ISO will likely come out around 2027, so ACLCA is developing interim guidance in the meantime.

Q4: How is the ACLCA work on the Open PCR Standard different from what ISO is doing in ISO 14077 for chain of custody and LCA? Would you consider it duplicative?
I see them as synergistic.

The ISO process takes longer—typically around three years—and it’s more international in flavor, with national mirror committees from different countries voting and participating. That’s really the gold-standard process.

The problem is, we don’t always have time to wait three years. We need guidance now. ACLCA is more nimble. It’s still consensus-based, but it’s a smaller group of experts, largely from North America.

We’re developing guidance as best we can, based on consensus, as an interim step until ISO 14077 is finalized.

We do have at least one member of our ACLCA group who is also on the ISO technical committee, so there is some cross-awareness. But the bottom line is: ACLCA is trying to move faster and provide interim guidance, which ISO can later complement or refine.

Q5: How can individuals and organizations participate in the public review processes for ACLCA and future development of PCRs?
Great question.

As part of the Open PCR Standard process, there’s a requirement for public consultations—typically a 60-day consultation period when documents are open for public review.

If you’re connected to ACLCA, you’ll probably automatically receive notifications. But I believe you can also go to ACLCA’s website and sign up under the Open PCR Standard to get updates on when documents are available.

I’d encourage you to do that if you’re interested.

Q6: Are ACLCA’s sister organizations globally, especially in Europe, working on this question as well, to your knowledge?
To my knowledge, no—I’m not aware of sister organizations taking on something exactly like this in the same way.

Q7: Do you see blockchain playing a role in mass balance chain-of-custody models?
It’s possible that it could.

This ties into how blockchain is being discussed for digital product passports in Europe as well. Anytime you have a chain-of-custody system, you’re tracking information through different steps in a value chain. A distributed ledger can make sense.

It could help with considerations around greenwashing and double counting by providing a robust ledger system for tracking materials. Right now, most systems rely on certificates and audits at each point in the value chain; a blockchain ledger could potentially provide a more integrated and transparent record.

Q8: How can mass balance credit method conform to the allocation procedures in ISO 14044?
Another great question.

The current allocation procedures in ISO 14044 don’t explicitly mention attribution, and that’s the first key point: attribution is different from allocation.

We’re developing guidance around where attribution fits into the existing hierarchy of allocation approaches in ISO 14044. Our working group is developing those guidelines and producing examples, which will be part of the document we publish next year.