Three straw products have public EPDs and their headline numbers are −101 kg CO₂e/m², −36.0 kg CO₂e/m² and +14.1 kg CO₂e/m³. None of these can be compared with another: the first is a 40 cm structural wall panel per m² (third-party verified), the second a 38 mm interior board per m² (internally verified only), the third loose straw insulation per m³ over its whole life. Put them in one table and the table is wrong before you read it.
This article puts them in one table anyway, with the columns that make the differences visible, so that the next time someone quotes “straw is −68” you can ask what product, what unit, which modules, and who verified it.
The short version
- EcoCocon wall panel (structural straw + timber, weighted average of six panel types, per m², MRPI 1.1.00555.2024, EN 15804+A2, third-party verified): A1–A3 GWP-total −101, GWP-fossil +17.4, GWP-biogenic −119 kg CO₂e/m². Biogenic content 31.5 kg C/m².
- Ekopanely E40/800 (compressed-straw board, 38 mm, 17 kg/m², per m², CENIA reg. 25918460, EN 15804+A2, internal verification only): A1–A3 GWP-total −36.0, GWP-fossil ≈ +4.3, GWP-biogenic −41.0 kg CO₂e/m². Biogenic content 10.7 kg C/m².
- UK straw as insulation (Environdec EPD3854, per m³ at 100 kg/m³, cradle-to-grave): GWP-total +14.12 kg CO₂e/m³, with 129.25 kg CO₂e of biogenic carbon stored.
- The negative totals are stored biogenic carbon (−1 in, +1 out). The comparable manufacturing figure is GWP-fossil: 17.4 and about 4.3 kg CO₂e/m² for the two panels.
- Vendor roundups that print “−68.006” and “26.348” for straw products without a unit, module or thickness are not usable numbers.
- All figures here are indicative, for early comparison, not for certification or compliance.
What do the three EPDs declare?
| EcoCocon wall panel | Ekopanely E40/800 | Straw insulation (Strawworks) | |
|---|---|---|---|
| Product | Load-bearing straw panel in timber frame, weighted average of six panel types | Compressed-straw building board, paper-faced | Loose/bale straw as insulation |
| Declared unit | 1 m² of panel (~40 cm) | 1 m² of 38 mm board, 17 kg/m² | 1 m³ at 100 kg/m³ |
| Programme / registration | Stichting MRPI, 1.1.00555.2024 | CENIA (Czech Environmental Information Agency), reg. 25918460, 1 March 2023 | Environdec International EPD System, EPD3854 |
| Standard | EN 15804+A2 | EN 15804+A2 | EN 15804 (Environdec) |
| Verification | External: Tim Mol, EcoReview | Internal: Jan Bareš, product and quality manager, Ekopanely CZ | External (Environdec requirement) |
| A1–A3 GWP-total | −101 kg CO₂e/m² | −36.0 kg CO₂e/m² | not separately stated |
| A1–A3 GWP-fossil | +17.4 | ≈ +4.3 (derived, see note) | not separately stated |
| A1–A3 GWP-biogenic | −119 | −41.0 | — |
| Biogenic carbon in product | 31.5 kg C/m² (≈ 116 kg CO₂) | 10.7 kg C/m² (≈ 39 kg CO₂) | 129.25 kg CO₂e/m³ stored |
| End of life (C) | C3 +112 total / +111 biogenic; C4 +6.2 | C1–C3 +9.5 total / +8.2 biogenic (C4 not declared) | included in cradle-to-grave total |
| Cradle-to-grave GWP-total | ≈ +23 kg CO₂e/m² (A–C, sum of declared modules) | ≈ −26 kg CO₂e/m² (A–C; the EPD’s own “Total” of −33.9 also adds module D, see note) | +14.12 kg CO₂e/m³ |
Sources: EcoCocon EPD (MRPI); Ekopanely EPD (CENIA); Strawworks, EPD3854 summary. Values rounded from the EPDs’ scientific notation.
Note on the Ekopanely table. The EPD’s results tables lead with a “Total” column that sums A1–A3, C1–C3 and module D (−7.47 kg CO₂e/m² for climate change). EN 15804 requires module D to be reported separately and never added to A–C, so the −33.9 headline is not a cradle-to-gate or a cradle-to-grave figure; A1–A3 is −36.0. The fossil row prints 5.02 as that D-inclusive total; subtracting the declared C and D fossil values gives roughly +4.3 kg CO₂e/m² for A1–A3, which is why that cell is marked derived. Module C4 is not declared, so the biogenic column does not fully return to zero within the table (+8.2 released in C3 against −41.0 stored). None of this is an error in the numbers; it is a layout that makes the headline easy to misread, and an internal verification means nobody independent has checked it.
Citation capsule: Three straw EPDs report on different bases: EcoCocon’s third-party-verified MRPI EPD gives −101 kg CO₂e/m² GWP-total (+17.4 fossil, −119 biogenic) for a structural wall panel per m²; Ekopanely’s internally verified CENIA EPD gives −36.0 for A1–A3 (about +4.3 fossil, −41.0 biogenic) for a 38 mm board per m²; the Environdec EPD3854 for UK straw insulation gives +14.12 kg CO₂e/m³ cradle-to-grave with 129.25 kg CO₂e stored.
Why are the totals negative, and does it matter?
Because EN 15804+A2 books the CO₂ a plant absorbed while growing as −1 kg CO₂e per kg when the straw enters the product, and +1 when it leaves. In A1–A3 you see only the first half. EcoCocon’s EPD shows the second half too: +111 kg CO₂e/m² biogenic released in C3 under its Dutch default incineration scenario, which brings the biogenic column back to approximately zero across A–C and leaves a net life-cycle figure of about +23 kg CO₂e/m², nearly all of it the +17.4 fossil plus transport and installation. The full mechanism is in biogenic carbon in EPDs.
It matters in one direction only: never compare a bio-based product’s A1–A3 GWP-total with a mineral product’s. Compare fossil with fossil. On that basis the two panels sit at 17.4 and roughly 4.3 kg CO₂e/m², which is low for a wall element and low for a board respectively, and both store carbon for as long as they stay in a building: about 116 and 39 kg CO₂ per m².
Citation capsule: Negative A1–A3 totals in straw EPDs are stored biogenic carbon booked at −1. EcoCocon’s EPD shows the release: +111 kg CO₂e/m² in C3, netting the biogenic column to about zero over A–C. The comparable manufacturing figure is GWP-fossil: 17.4 kg CO₂e/m² (EcoCocon wall panel) and about 4.3 kg CO₂e/m² (Ekopanely 38 mm board, derived from the EPD’s D-inclusive total).
Why can’t these three be compared with each other?
Different functions. A load-bearing, insulating wall panel; a non-structural interior board; loose insulation. You would never put them in the same line of a bill of quantities, so their per-unit carbon has no common denominator either. The right comparison for EcoCocon is other external-wall systems per m² at equal U-value; for Ekopanely, other boards per m² at equal thickness; for straw insulation, other insulations per m³ at equal thermal resistance.
Different units. m² of a 40 cm element, m² of a 38 mm element, m³ of loose material. Converting Ekopanely to m³ (17 kg/m² at 38 mm ≈ 447 kg/m³ by mass, or ÷0.038 by volume) or EcoCocon to m³ is arithmetic you can do, but it produces a number the EPD did not declare.
Different scopes. EcoCocon and Ekopanely declare A1–A3 with C and D; the Strawworks summary gives a cradle-to-grave total without separating fossil from biogenic, so its +14.12 already includes the release. Its stored 129.25 kg CO₂e/m³ is the delay benefit, not part of the total.
Different verification. Two of the three are externally verified. One is not. That is not a detail; it is the difference between a number someone independent has checked and a number the manufacturer has checked.
This is also why vendor “straw material” roundups that list figures like −68.006 and 26.348 with no unit, module, thickness or verifier are not data. They may well be lifted from real EPDs, but stripped of their basis they cannot be used for anything.
Citation capsule: Straw EPDs cannot be compared with each other because they declare different products (structural panel, interior board, loose insulation), different units (m² at 40 cm, m² at 38 mm, m³), different scopes (A1–A3 with C/D vs cradle-to-grave total) and different verification levels (two external, one internal). A usable straw figure states all four.
How does Elementa use these figures?
Elementa’s impact classes are indicative bands for comparison at concept stage, derived from EPD and generic-dataset values. For bio-based products the class follows GWP-fossil, and the stored biogenic carbon is shown as a separate quantity whose value depends on the element’s circularity pathway: retained or reused, the storage holds; replaced and incinerated, it does not. The data source and its verification level are shown per element, so an internally verified EPD is labelled as such rather than silently treated as equivalent to an external one.
None of this replaces the EPDs. It is a way of reading them consistently before the formal assessment, which is when a certified LCA takes over.
Citation capsule: Elementa assigns bio-based elements an indicative impact class on GWP-fossil, reports stored biogenic carbon separately as pathway-dependent, and labels each element’s data source and verification level, so internally and externally verified EPDs are not conflated.
Frequently asked questions
What is the embodied carbon of a straw wall panel?
EcoCocon’s third-party-verified EPD (MRPI 1.1.00555.2024) declares −101 kg CO₂e/m² GWP-total for A1–A3, of which +17.4 is fossil and −119 is stored biogenic carbon. Over the full life cycle with incineration at end of life the net is about +23 kg CO₂e/m². The panel is a ~40 cm load-bearing straw-and-timber element.
What is the embodied carbon of a compressed straw board?
Ekopanely’s EPD (CENIA, reg. 25918460) declares −36.0 kg CO₂e/m² GWP-total for A1–A3 for the 38 mm E40/800 board, with −41.0 stored biogenic carbon and roughly +4.3 fossil (the printed 5.02 is a total that includes module D). The EPD is internally verified; treat the figures as indicative.
What is the GWP of straw bale insulation?
Environdec EPD3854 for UK straw at 100 kg/m³ gives a cradle-to-grave GWP-total of 14.12 kg CO₂e/m³ with 129.25 kg CO₂e of biogenic carbon stored. Compare it with other insulations per m³ at equal thermal resistance, not per m².
Are straw panels carbon-negative?
Cradle-to-gate the EPD totals are negative because of stored biogenic carbon. Whole-life, if the straw is eventually burned or landfilled, the stored carbon is released and the net is positive (about +23 kg CO₂e/m² for EcoCocon). The panels are carbon-storing while in use, which is real and conditional on what happens at end of life.
Can Elementa certify these figures?
No. They are the manufacturers’ EPD declarations, two externally verified and one internally. Elementa reads them into indicative impact classes with the verification level labelled. Certification and compliance need the EPDs and a qualified assessor.
The takeaway
Straw has good numbers: 17 and about 4 kg CO₂e/m² of fossil emissions for a structural wall panel and an interior board is low, and both store carbon while they stand. The problem is not the numbers, it is the way they get quoted: a total that is mostly storage, a unit that goes unstated, a board compared with a wall, a “Total” that quietly includes module D, an internal check passed off as verification. Ask for product, unit, module and verifier, and the three EPDs stop contradicting each other.
If you want bio-based and mineral options compared on fossil emissions, with storage and verification shown per element, before formal assessment, start a project.