Our pilot project demonstrates the full value chain for ERW at € 230 per ton of CO₂ (with € 100-150 in sight)

In our Enhanced Rock Weathering (ERW) pilot project with 1217 tons of basalt we are demonstrating that all necessary tools, players, supply-chain and knowledge are already available today to build a working, profitable carbon dioxide removal (CDR) project at a competitive price of € 230 per ton of CO₂e in Germany. 

In Part 1 of this blog post series we will describe the concepts, in-field work and financials all the way until the certification. Part 2, coming soon, will be about the sale process for the certificates that we have created.

Here is the story…

We started working on rock weathering projects in fall 2020. Our first ton of basalt was spread on a field by hand in March 2021. Since then we x10’ed the amount of basalt with every new project. 1 ton, 10 ton, 100 ton. In fall 2022 this culminated in a ready-to-scale demonstration project for CDR using 1217 tons of basalt. 

Our proof-of-concept-project is however more than just a rock-spreading exercise. It has some special features:

• Our project demonstrates today’s economics of the complete value chain from basalt mine to logistics, farmers, certification and finally sale/tracking by the dedicated carbon tracking and sales service Carbonfuture. It shows that all involved partners can be profitable or (at least) break even while selling the credits at a competitive price of ca. 230 Euro per ton of CO₂e with further cost reduction potential of 50%.

• Our project is the world’s first third-party certified ERW project using a new ERW certification methodology (PDF) created by our partner Ithaka Institute for Carbon Standards International which involves an independent in-field certification of rock applications by q.inspecta.

• Our project will capture and permanently store ca. 360 tons of CO₂e with ERW. Long-term storage is 100% guaranteed by conservatively assessed ERW.

• There were no capital investments (CAPEX), all the required resources, machinery and physical infrastructure already exist today as part of day-to-day mining, logistics and agronomic operations - which clearly distinguishes ERW from most other NETs.

This successful demonstration of the full value chain from basalt mine to carbon-sink certificate lays the foundation for rapid scaling.

What “covering the full-value-chain of ERW” means

Consider our flow chart of the steps necessary to do ERW projects. In our demonstration project we - together with our partners - have performed all the steps that are marked with a blue arrow:

Each of the boxes in this graphic could be an organization/company of its own. In general we don’t believe that all rock weathering companies in the future should perform all these steps themselves, the industry will likely consist of specialized players (especially when trust/governance is involved, e.g. certification vs. business needs, see below).

The colors of the boxes show their technological readiness level (TRL)  as far as we have assessed it. A color legend is shown on the lower right.

The key question: How do we do MRV and certification?

MRV (monitoring, reporting and verification) and certification are key challenges for all negative emissions technologies. How do you actually measure the amount of carbon dioxide that you draw down? This is especially challenging for enhanced rock weathering on croplands.

The initial version of our certification methodology created by Ithaka works without in-field measurement. It applies a very conservative model for the calculation of ERW-based CDR. It is based on peer-reviewed papers and applies adequate security margins to guarantee reasonable carbon drawdown rates with high confidence. The huge security buffers on the other hand immediately reduce the economics of the whole process. That is why the certification allows for updates of the calculations as soon as new data is coming in. Process emissions during rock powder production and transport/spreading are of course considered in the life cycle analysis of the complete carbon budget.

The “Global Rock C-Sink” certification guidelines by Ithaka Institute (PDF) have been published on Oct 31st 2022. It has not been formally announced yet, though (will happen in a few weeks). Our considerations for rocks and soils are mentioned there, too. The first certificates for the CDR from our project have been issued by q.inspecta on Nov 2nd 2022.

The new certification methodology considers the specific nutrient and trace-element content of the deployed rock dust, as well as the field's soil characteristics, to ensure application rates that are safe and beneficial for the agricultural system and in accordance with all relevant European regulations. It is imperative that cropland-based ERW applications are carried out in such a framework, have only positive effects to the agronomic system and thus can fully be acknowledged as a beneficial agricultural practice – not as a CDR-focused burden to be carried by the farmers and the food system. This foundation is crucial for acceptance and scalability.

Why is third-party certification important?

We are concerned that projects with bad reputation might hurt the trust of the public in ERW in general. In our view therefore it is vital for the credibility of purchased certificates that the company who executes a CDR method is not the one which certifies and validates the actual CDR and/or the one that creates the certificate and sells it. Both parts of the challenge to scale up rock weathering, i.e. MRV on one side and up-scaling on the other side, have different strategies/needs and are likely hard to combine in one organization responsibly due to conflicting interests (e.g. grow fast vs. measure exactly). For optimal governance separate institutions to us seem to be the best solution. 

Scientific follow-up by Project Carbdown

We are combining the pilot project with our scientific efforts to measure ERW at Project Carbdown. We are using in-field measurements, sampling and extensive pot/lysimeter experiments to follow up on the actual weathering rates in the cropland fields. The actual soils from the fields used in this project will be included in a large set of pot/lysimeter experiments in our greenhouse lab. 

In this extensive greenhouse experiment starting in winter 2022/2023 the weathering kinetics will be assessed for each soil using several measurement methods to quantify captured CO2. These will include analyses of weathering products in leachate, quantifications of remaining rock in the soil as well as measurements of gas fluxes and precipitation of secondary minerals (which can potentially reduce the amount of captured CO₂ by up to 50%), e.g. using isotope analyses. The experiments are planned to run for 24 months or more and will involve hundreds of pots/lysimeters allowing us to better understand the uncertainty ranges in realized CDR-potential for different soil/rock combinations and rates.

Optimized for speed, not for economics

For this pilot project we solely focused on demonstrating the current status of ERW practice, involving all parties from “cradle to grave”. To speed up the project we did not focus on cost-reducing optimizations. This resulted in a sales price of about € 230 per tonne of CO₂. Many parameters,  however, can be optimized. 

We are using off-the-shelf Eifelgold “Brechsand” with grain sizes up to 2,000 microns supplied by RPBL at a special discounted price per ton. In the future rock cost could be lowered e.g. by using cheap, pelletized waste basalt dusts (there are plenty available). 

The main cost drivers remain the logistics: most of our fields were 300-400 km away from the mine, one field even 560 km, which isn’t ideal at all. Costs (and CO₂ emissions) could be substantially lowered by choosing fields closer to the mine or by using ships and trains instead of trucks for most of the transport, especially for larger amounts of rock. Finally, we should be able to progressively lower the carbon removal security margins in the future through improved scientific understanding and through data being collected as we speak, which will also have an effect on pricing.

One of the reasons to select Eifelgold basalt was avoiding delays due to pre-application lab tests or approvals from government agencies. We can confidently say that this project is environmentally safe since we use a rock type that has been certified for fertilizer use in the EU for decades. Eifelgold is even listed in the allowed amendments for organic farmers in the Demeter group. Nevertheless we are monitoring for heavy metals, etc. in our follow-up lab/greenhouse experiments. 

Choosing “Eifelgold Brechsand” made us faster for this project, but for future projects it may be worthwhile to consider other rocks as well. 

How is the amount of stored CO₂ calculated?

The “Eifelgold” basalt has a theoretical CDR capacity of 419 kg CO₂ per ton of rock. The theoretical CDR capacity of a given rock can be expressed as a function of its metal content (alkali- and alkali-earth-metals). The employed method is using a well established formula to calculate the theoretical CDR capacity, based on the assumption of an incongruent release of metal cations, only considering calcium, magnesium, potassium and sodium (see certification guidelines, Chapter 2.2.1).

Deploying different safety factors and defining requirements to the agro-climatic conditions of a land-unit to be admissible for rock powder applications, the theoretical CDR capacity is translated into a certified Rock C-sink potential. The guidelines exclude land-units of agro-climatic conditions fostering secondary clay formation, which would impede a full realization of the CDR capacity, due to immobilization of metals (certification guidelines Chapter 3). A safety factor of x0.9 is applied to the CDR capacity, addressing the remaining uncertainty resulting from potential clay formation (certification guidelines, Chapter 2.2.1). To address potential downstream losses of dissolved inorganic carbon, two more safety factors are applied. To address the potential formation of persistent calcium carbonate a conservative safety factor of x0.9 is applied. Lastly, a safety factor of x0.86 is applied to account for the CDR efficiency once dissolved inorganic carbon is reaching the ocean via riverine systems. Here losses can be expected from oceanic carbonate equilibria (certification guidelines, Chapter 6-6.1).

The CDR is certified independent of the temporal dynamics of C sequestration, as for prevailing uncertainties regarding the exact carbon sink curve (certification guidelines, Chapter 7-7.1).

About Eifelgold, the rock that we used

We use a rock source which is certified as soil amendment material. The brand is “Eifelgold” from “Rheinische Provinzial-Basalt- und Lavawerke GmbH & Co. oHG (RPBL) Werk Langacker”. Before our pilot project we had tested Eifelgold in fine (<200 microns) and coarse (<2000 microns) configurations.

We found that in this case counterintuitively the coarser material has a larger surface area and in our ongoing xxl lysimeter experiments it seems at least not to weather slower than the all-fine stuff. 

Lab analysis (BET) showed that the available surface area for reaction of the coarse basalt (2.6 m²/g) is comparable and even higher than the finer material (1.8 m²/g). This seems due to a higher roughness of the material, likely due to how it was milled. As BET surface area is one of the key controls for the reaction rates and the mining of the coarse material needs less energy, this material was chosen.

It is important to know that the coarse grains are also much easier to work with at scale (transport, storage, spreading), e.g. it can get wet without clumping. See our blog.

Show me the money!

There are several important numerical dimensions of a CDR project:

• € per ton of basalt incl. transport (<= our major cost driver)

• € per ton of captured CO₂  (<= what we can sell it for)

• tons of CO₂ and basalt per hectare (<= connects the other two)

Our cost for 1217.1 tons of basalt was € 57,021 including transport to the fields (all € figures are excluding VAT). Which means we have paid 46.85 € on average per ton of basalt or € 159 per ton of CO₂ captured. Two thirds of the cost is only the transport of the basalt via trucks. This means it is possible to reduce the cost by 50% or more by reducing the distance and/or using less expensive means of transport. Additional cost reductions may be possible by using cheaper rocks (e.g. mine wastes).

With the certificates issued by q.inspecta we have proof that we have captured 359 tons of CO₂, which is 70% of the chemical (stoichiometric) potential of 1217 tons of basalt (509 t of CO₂ at 419 kg/t) due to our conservative methodology. This ratio will likely become higher over time as we reduce the uncertainties of ERW on croplands, which will add additional certificates later. The cost per ton of CO₂ could be lowered by ∼20% if science can demonstrate that the capture is closer to ∼85% of the rock’s potential.

By combining the two optimization methods (improved logistics and better/more exact MRV) one can theoretically reduce the cost of basalt+transport per ton of CO₂ captured by 60%. This means that rock costs below € 100 per ton of CO₂ captured come into reach.

There are potential positive side-effects of adding basalt to fields, e.g. lower fertilizer and lime requirements, increased plant health, improved water holding capacity, improved crop yield, etc. We have not assessed or taken these into our financial calculations for our pilot project. They will have to be investigated further and will eventually become a part of future financial models for ERW, improving the economics further.

Apart from the rock there are also other costs to be considered which added up to € 66 per ton of CO₂ in our case.

As of today our full cost was € 80,707 for the project or € 224 per ton of removed CO₂ while covering all costs for all the partners involved. Nobody made a real profit yet, but that wasn’t the goal of the pilot project. Each and every step has considerable optimization potential!

We have shown that in 2022 you can do a full-life-cycle ERW project in Germany at ca. € 230 per ton of CO₂ (cheaper than most other offerings of upcoming NETs today). And we can argue that the full cost per ton of CO₂ can actually be lowered to € 100-150 in the near future. This cost range is ok since we expect a market sale price of around € 150-200 per ton of CO₂ on the voluntary market anyway for the next few years.

What were our project-related emissions?

At present the project is exclusively deploying basalt rock powder originating from mining-tails (by-products of past mining activities). No additional emissions occur from such a scenario. If rock powder was produced exclusively for ERW applications, a proportional share of the scope 1-3 emissions of the mining facility will be attributed by the methodology. The attribution of emissions will be carried out according to the developed carbon sink certification guidelines.

In our planning we had considered emissions from transport and field application, as follows - to be calculated on a case-by-case basis. Considering mean transport distances of 250km, a mean transport emission factor of 111g CO₂/t/km (truck, Germany)  and 4 kg CO₂/t for field application, each delivered t of rock powder will be attributed with carbon expenditures equivalent to: 250* 0.111 + 4 = 31.75 kg CO₂. In total 1200 t * 0.03175 t/t = 38 t CO₂. 

In the end we calculated the actual emissions to be 44,6 tons CO₂, due to the fact that we drove more truck kilometers than we had planned. This is less than 10% of 1217 t basalt’s CDR potential of 509 t CO₂. In summary: The mining and transport emissions are one order of magnitude smaller than the CDR effect, even with 300-500 km transport distances. This will only get better in the future with more green energy, electric trucks and optimized logistics.

Photos from the spreading

Who did all this?

The following organizations  were involved in the project:

• a privately funded, independent NET-focused organization (Carbon Drawdown Initiative),

• a scientific consulting team of 25 scientists from six universities in Europe and the USA (Project Carbdown), 

• an independent institute (Ithaka Institute), that has already created a trusted CDR certification methodology for biochar (European Biochar Certificate EBC), 

• an independent certification organization (q.inspecta),

• a basalt company (RPBL), 

• a leading platform and marketplace for high-quality and impactful carbon removal credits (Carbonfuture). The Carbonfuture platform provides full digital tracking of carbon sinks, providing verifiable end-to-end carbon removal accounting and flexible trading, and 

• nine farmers in Germany.

People involved

• For Carbon Drawdown Initiative: Dirk Paessler, Founder and CEO; Ralf Steffens, CTO.

• For Ithaka Institute: Johannes Meyer zu Drewer, lead author of the guidelines for ERW certification and Dr. Nikolas Hagemann, CEO and scientific director.

• For Carbon Future: Dr. Hannes Junginger-Gestrich, Co-Founder and CEO; Dr. Matthias Ansorge, Co-Founder and CTO.

• The scientists of Project Carbdown, our MRV science project: Prof. Dr. Jens Hartmann (University Hamburg), Prof. Dr.  Jelle Bijma (AWI), Dr. Mathilde Hagens (Wageningen University), Dr. Ingrid Smet (Fieldcode), Dr. Maria-Elena Vorrath (University Hamburg), Prof. Dr. Philipp Pogge von Strandman (University Mainz), Prof. Dr. Johannes Barth (University Erlangen), Prof. Noah Planavsky (Yale University) and many others.

Stay tuned for part 2 of this story!

Continued in Part 2 (coming soon), where we will explain how we sold the certificates via Carbonfuture.

Update October 2024

Unfortunately no viable option has arrived yet to get CDR certificates from this EW project certified. Thus us our project is still not certified/sold yet.