Biochar in Portugal: Making and Using It on the Farm

Portugal is charcoal made from biomass — essentially partially burned organic material. But unlike charcoal you’d use for a barbecue, biochar is made specifically to stay in the soil or be used as a soil amendment. Read more about biochar in Portugal.

When we’re cutting eucalyptus and mimosa for firewood, we end up with a lot of branches we can’t burn efficiently in our stove. A few years back we realised we could turn that waste into biochar, use it to improve our animal bedding, and then feed it straight into our compost system. It’s become a simple closed-loop process that barely adds any extra work but genuinely improves how our farm cycles its resources.

What is biochar, really?

Biochar is charcoal made from biomass — essentially partially burned organic material. But unlike charcoal you’d use for a barbecue, biochar is made specifically to stay in the soil or be used as a soil amendment. The key thing about biochar is its structure: it’s got a huge surface area packed with millions of tiny pores. This makes it incredibly good at holding water and nutrients, and at hosting beneficial microbes in the soil.

In Portugal especially, where a lot of our soils are acidic and depleted, biochar can help. It doesn’t fix poor soil on its own, but it acts like a sponge and a living space. Add it to compost or use it in your beds and it improves water retention and soil life. It also locks carbon in the ground for a very long time — we’re talking centuries.

How we make Biochar Portugal

We do it the simple way: dig a hole, make a bonfire from our waste branches (mimosa and eucalyptus mostly), let it burn down to charcoal, and then smother it with earth to stop the burn. That’s it. It’s not elegant but it works.

There are better methods if you’re serious about scale. A proper biochar kiln — things like a top-lit updraft kiln (TLUD) or a retort system — gives you more control, cleaner burns, and better yields. We’ve looked into building one, and it’s on the list, but for now the ground bonfire does the job for 5 cubic metres a year, which is what we use.

The basic steps:

1. Pile branches in and around a dug pit
2. Set it alight and let it burn down to charcoal (couple of hours)
3. Cover the whole thing with soil and earth to smother the flames
4. Let it cool completely (usually overnight)
5. Dig it out and break up the charcoal pieces

Using biochar as animal bedding

Raw biochar can smell quite sharp and dusty, so we don’t put it straight on the animals. Instead, we use it mixed into deep bedding for our sheep and chickens. The biochar absorbs moisture and ammonia — the smell that builds up in animal housing. It also activates as it absorbs the animals’ manure and urine, picking up nutrients and microbes.

We add a layer of biochar mixed with our usual bedding materials (hay, straw, wood shavings, whatever’s available), and the animals live on top of it. Over weeks and months, they walk it in, their manure activates it, and the whole thing gets richer.

Building compost from biochar bedding

After a few months, the spent bedding — now full of activated biochar, animal manure, and microbial life — goes into our compost pile. This is where the closed loop gets interesting. The biochar in the compost acts as a microbe haven and helps the pile hold moisture and nutrients. When we finish the compost and spread it around the barn and in our growing areas, the biochar goes into the soil with it.

We’re not measuring this scientifically, but anecdotally, compost made with biochar-bedding feels richer and breaks down more consistently than compost without it.

Why this matters for Biochar in Portugal

Portuguese soils, especially here in central Portugal where Keela sits, tend to be acidic and often depleted after centuries of agriculture. Most of our land needed serious building up. Biochar won’t fix acidic soil on its own — you still need to manage pH properly — but it helps. It acts as a buffer, holds onto the good stuff you add, and creates a living space for the microbes that actually build soil fertility.

It also fits neatly into a permaculture approach: we’re not importing expensive amendments. We’re turning our own waste into something useful, activating it through our animal systems, and cycling it back into the land. That’s the whole point.

What’s next

Making biochar is simple enough that anyone with waste branches can try it. If you’ve got eucalyptus or mimosa clearings, a bonfire, and some animals, it’s worth experimenting with. We’re still learning — proper measurement of what biochar actually adds to our soil would be useful, and building a kiln to improve our process is still on the list.

If you’re interested in how we think about soil, animal systems, and closing loops on a farm, that’s exactly what the Permaculture Design Course explores. Check out the course page or get in touch if you’d like to know more.