The Zero Waste Coffee Project

NetZero: coffee husks, biochar and a 1 million dollar prize. An interview with Axel Reinaud

A look at the Biochar International Initiative website shows us that the production and use of biochar and syngas is rapidly growing in importance. Biochar is not only a great soil amendment and excellent for CO2 sequestration, but syngas can be converted into heat and electricity.

However, in the coffee world, the by-products of which would be ideal for the extraction of biochar and syngas (and also bio-oil) via pyrolysis, this has not yet quite arrived. There have been a number of scientific papers and projects, e.g. in Ethiopia (1), Uganda (2) and Ecuador (3), but real applications have not yet been achieved. However, the Pyrolysis-Flox technology (4) developed in collaboration with Ökozentrum Schweiz and Sofies could be promising. It produces biochar and syngas from coffee husks and pulp in an extremely clean way: the energy (power & heat) is used to operate mechanical coffee dryers called guardiolas, and the biochar is used as a soil amendment. First applications exist in Vietnam (5) and Peru (6).

The first real attempt to use coffee husks on a larger scale as feed stock for pyrolysis has recently been made by NetZero, a young company based in Paris. NetZero's primary concern is the carbon removal from the atmosphere. I recently had a conversation with one of the co-founders, Axel Reinaud. This was 2 weeks before NetZero was awarded by XPRIZE & the (Elon) Musk Foundation with a $1 million prize in their "XPRIZE Carbon Removal" competition. Here is my interview with Axel Reinaud:

Hello Axel, I know your time is precious; for that let’s dive right away in the subject. I think it’s not exaggerated to say that even with a magnifying glass it’s impossible to find applications of pyrolysis in the waste stream of the coffee chain. But you want to change this?

Well, we are a tiny little piece within this huge amount of coffee waste, or maybe better to call it coffee by-products. Technically we we're not limited to coffee, but we decided to focus 100% on it initially. The main reason for that is that my partner and co-founder is the owner of Synergie Nord Sud, the largest coffee processing plant in Cameroon, located in Nkongsamba, western Cameroon. Because of that we have access to lots of coffee husks and we said, okay, let’s go for it, let’s start in Cameroon! But again, technically it’s no problem to switch to other types of biomass.

You use the husks of the sundried coffees I assume.

Yes, that’s correct. We use the husks of Robusta coffee which also includes the parchments. In Cameroon they grow mostly Robusta, but husks from Arabicas would do the same job.

Does the amount of husks of a harvest season last for a whole year? I mean, for an amortization of your equipment it should ideally run all over the year.

We aren’t actually looking from one harvest season to the next, but from one "de-husking season" to the next. The peak of available husks lasts between early April to the end of June, but de-husking happens over the course of the whole year. On top of that, we store the coffee husks produced during the peak of the season, to use during the lower production times.

Which means that you are not only storing the husks, but also the whole, dried coffee cherries, and when a certain quantity of that coffee is sold, then the husks are removed and become available to you.

Exactly! We can say the coffee is "a storage of value" for the farmers, and for us as well.

So, you use exclusively the husks of sundried coffees?

Yes. Washed coffees are very different, the pulp is too wet for pyrolysis. It's not suitable.

Well, I mean, you could dry the pulp, but that's a lot of extra work to do and would raise the costs. My understanding is that the energy output from pulp is less compared to that from husks or other organic waste like straw, wood etc. For that, countries like Brazil, Vietnam and Ethiopia with their large volumes of sundried coffees must be suitable for your technology. Do you have plans to expand to any of these countries?

Absolutely! We already have plans to build our second plant, this time in Brazil. But first we need to stabilize our model. As you know, this is very early days, the company is just a year old, so we have to go step by step. We need to see how it works, learn, and then we start building more plants. But we're not immediately going to spread to all countries because this would be difficult to manage. For probably the next year or two we’ll stay in Cameroon and Brazil, and then I can imagine to expand. It will be an iterative process, and yes, countries like Vietnam and Ethiopia are on our expansion list.

Which affords investments...

Exactly! So, basically there is a huge potential but we need to go slowly at the beginning. We have to learn and improve our model.

I want to understand a bit more the economic side. Let’s start with the husks: do you get them for free or do you pay for them?

The husks are not free, but they are relatively cheap, at least for now. In return, the farmers get the resulting biochar for a very low price as well, it's a circular model. We need to find the right economics: the lower the costs of the feedstock, the lower the costs and price of the biochar.

Is this model profitable?

We believe it’s profitable, although we still have to prove it. I mean, the economic parameters are tricky; we are aware of this, but we think we can make it work.

How many tons of coffee husks can you turn into Biochar with your equipment in a year?

There's a lot of coffee husks to work with! You have a husk:bean ratio of almost 50:50. At our site in Cameroon, about 10,000 tons of husks are generated as by-product per year. If our machine runs at full capacity, we can turn 8,000 tons of these husks into biochar over the course of the year. I don’t know exactly the volume of sundried coffees that is produced worldwide annually, but it’s a lot. We can install lots of machines!

Those are some impressive numbers!

Yes, it’s not bad! But again, the volume of husks is already there.

In Cameroon and elsewhere! Which brings us back to Brazil, Vietnam, Ethiopia etc.

Exactly! That's why we went to Brazil. There is this big opportunity. And one day maybe we'll go to Vietnam or Ethiopia.

And everyone there will ask you: "How much CO2 will be kept out of the atmosphere compared to burning the husks, or just letting them decay?"

About 3,300 tons of CO2 per year is stored in the biochar if we run on full capacity.

How do farm and mill owners react when you present them your project and these numbers?

People are very interested! Everyone is sensitive to the environmental concerns, everyone's sensitive to the price of fertilizers, and everyone's sensitive to the trend toward more value-added coffee. We had initially thought that we would have to push hard for people to accept our model, but actually it's the opposite, they're asking for it! As soon as they understand the concept, they want it. Given that we propose something that will have a real agronomic value, they make their calculation, and very quickly they realize it's a good deal.

But to operate economically you have to collaborate with larger farms or co-ops...

We can collaborate with cooperatives, or we can work with a mix of large farms and small farmers, the structure of the coffee production varies by country and even by region. We cannot deal individually with, let’s say, 2000 smallholders, that’s impossible. But usually you have some kind of focal point, whether it's a large farm, a cooperative, a mill or a de-husking facility. There are ways to find the right type of partners.

How large is the collection area you need to be economically sustainable?

I would say, roughly estimated, about 10-15 km squared would be enough to get the volume of husks that we need.

How do I have to imagine the collaboration with a large coffee farm, a co-op, a mill, etc.?

The coffee producers are our clients, so to say. The operation to produce biochar and syngas is fully owned by NetZero. We do the plant design, we buy the equipment, do the operations, we do everything.

This model of collaboration and processing allows you to bring your whole idea at a scale that one day might have a measurable impact regarding CO2 removal!

That’s what we are hoping for! You know, you can say it's kind of an equilibrium between being big enough to be efficient, and being small enough to stay close to the sources of the biomass. We don't pretend to have the full knowledge, or that we have the ultimate ratio in our hands just yet. We're going to learn, we will develop. We know all this will take some time, and when we are ready, we’ll scale up.

Generally, with pyrolysis you produce biochar, syngas, and usually oil as well. The biochar, as you mentioned before, is sold for a low price to the suppliers of the husks. What are you doing with the oil and the gas?

Due to our technology there is barely any oil left. The gas will be used to generate electricity. We will feed the generated electricity into the grid. We are working on that process. I would say in about three to four months we can start.

I couldn’t find anyone using coffee husks for pyrolysis on a commercial basis. Is NetZero really the only company doing this?

To our knowledge, yes. Maybe there are some other people working with coffee husks in the background, but to our knowledge, it’s so far only us. There are a lot of people producing biochar in North America and Europe at a large scale with different feedstocks. But our smaller scale model, with just coffee husks, I haven't seen that elsewhere. We are the first ones doing this, but we hope to be copied because that would mean that we found a winning formula.

A question regarding the biochar: is biochar and its application well known in the area you are working in?

No, biochar is unknown; only a few people have heard of it and had a vague idea. For that we developed a model to train the farmers who supply us with the husks. It’s still on small scale and we were tinkering with that for a while. The first set of farmers is trained. But since farmers often first want to see how, and if, it works, we established kind of test plots were people just come over and watch how the biochar is applied to the soil. Then they might take a bit of biochar back with them and apply it to some short rotation crops, and if it works they might say okay, maybe we can use it for our coffee fields when we replant trees.

What helps us ultimately to convince farmers to apply biochar to their soil is the steep increase of the prices of fertilizers. The farmers say, ok, what are the alternatives, and we say okay, maybe we have something you want to try. We hope that farmers that attend a training session will teach their neighbours, friends or family members; and that the "by-stoppers" are curious enough to try it out themselves. We will see how it evolves or if we have to invest more to get the word out. We are aware that this will not be a fast process. We don’t expect things happen overnight.

And this process will happen also at different speeds...

Exactly, some people are more innovative and might be faster, and some will go slower. That's the inertia of the system, especially in agriculture.

Last question: how fast did it go with your decision to start this adventure?

I was interested in biochar and climate change for a long time. My father was working on such topics, and so, at some point I decided okay, let's give it a try. I started thinking of what concrete action I could take. I was talking to many other people, and gradually the idea emerged. It didn't come like this, overnight. And not to forget: I also had to quit my job at Boston Consulting Group. It was quite a lot of thinking; and lots of work to design the model. Now, a bit more than a year later, we're trying prove that our idea works. It's a field where lots of people have been working or thinking about possibilities, but not too many people have done it at scale, and definitely not in a country like Cameroon. For that we are still exploring and discovering, as there's very little concrete experience out there. It’s a long but exciting way to go.

Axel Reinaud, thank you so much for your precious time!


1-Coffee-husk biochar application increased AMF root colonization, P accumulation, N2 fixation, and yield of
  soybean grown in a tropical Nitisol, southwest Ethiopia, 2019

- Cornell and Jimma University collaborative partnership. Development of indigenous biochar-based fertilizers.
- Effect of biochar on soil properties and lead (Pb) availability in a military camp in southwest Ethiopia, 2015.
- ETHIOPIA - B4SS PROJECT
2 Pyrolysis of Coffee Husks for Biochar Production
3 Potential for Farmer´s Cooperatives to Convert Coffee Husks into Biochar and Promote the Bioeconomy in the North Ecuadorian Amazonas, 2021
4 THE PYROLYSIS?FLOX TECHNOLOGY - Clean heat and biochar from agricultural waste
5 Pyrolysis technology for Vietnam’s coffee industry: a resource efficient an climate positive technology
6 Pyrolysis for coffee pulp valorization

A comprehensive overview of pyrolysis with coffee by-products is given by Kathleen Draperin her White Paper "The Potential for Biochar to Improve Sustainability in Coffee Cultivation and Processing".