Blogue SHIFT

By Alexandra Bussler

The municipality of Coruche lies about 80 km northeast of Lisbon in the district of Santarém, in Leziría do Tejo. Despite its only 20.000 inhabitants, it is one of the largest municipalities in Portugal, stretching across 1.120 km². Due to its vast cork tree plantations, Coruche has come to call itself the cork capital of the world: as the largest cork producing district it fabricates 5 million corks every day.

However, not only cork is produced in Coruche. Santana do Mato, one of the municipalities’ six parishes, hosts one of the last remaining traditional charcoal industries in Portugal following centuries-old traditions. Since prehistoric times, mankind uses charcoal as energy source (cooking, BBQ), activated carbon (filters), biochar for soil fertilization, or in steel industry, drugs or silicon-making processes (e.g. photovoltaic panels). It results of a process called pyrolisis, burning wood in a low oxygen environment. The wood is split into charcoal, water vapour, methanol, acetic acid — but also tars and non-condensible gases are released: hydrogen, carbon monoxide and CO₂. It is argued that charcoal produced from biomass (wood) is renewable, since biomass can regenerate relatively quickly. However, assessing its environmental impacts is key to know how sustainable it really is. The major impact stems from CO₂ emissions from unsustainable logging, as well as from incomplete combustion releasing the major GHG methane (CH4) and black carbon (BC). Around 1–2.4 Gt of worldwide CO2 emissions come from traditional wood energy (fuelwood and charcoal), and these contribute approx. 2–7 percent to global anthropogenic emissions. In Portugal alone, an estimated fifth of all CO2 emissions stems from biomass.

The most common ways to produce charcoal involve using earth pits (covering a pit full of wood to seal up the chamber) or kilns (covering a pile of wood on the ground with sealing material). However, these methods have low conversion efficiency and emit a serious amount of environmentally and health-critical substances. Today, the most advanced methods are steel kilns or retort kilns. Retort kilns improve efficiency and reduce GHG emissions substantially via an additional high-heat combustion chamber.

In Santana do Mato, charcoal is produced in semi-industrial brick ovens inspired by the Brazilian beehive kiln type. They are circular, with an arched roof and are built of ordinary bricks. Here, concrete and earth are used for sealing. Small chimneys currently allow the escape of the volatiles during carbonization.

Fonte: Museu da Paisagem de Coruche – imagem 1 e 2; Rosa Lopes (Câmara Municipal de Coruche) – imagem 3

Currently, 321 brick kilns are operated by around 30 entrepreneurs. Around 17.575 tons of charcoal are produced yearly. The actual conversion rate is of 1000 kg of wood for 300 kg of charcoal. Although regulated, the working conditions in this industry are below standards.

To obtain high-quality charcoal with low toxic components and minimized GHG emissions, specific technical requirements have to be followed: i) one must be able to control the different heat phases; ii) the optimum maximum temperature has to be reached. Otherwise, charcoal becomes corrosive and unable to burn with a clean, smoke-free flame. While today in Portugal the development of sophisticated kilns already allows to produce charcoal ecologically, without CO2 emissions, toxins-, tar-, smoke- and waste-free, Santana´s ovens aren’t equipped with these new technologies. Environmental impacts are therefore expected to be significant. However, this makes Santana’s charcoal relatively cheaper than the more sustainable Portuguese products. This is why the industry is still surviving, despite producing a lower quality product.

In Portugal, no comprehensive emissions inventory of the national charcoal production has been made. Neither do we know the actual environmental impact of Coruche’s charcoal industry. Under the umbrella of the research project BEACON, the municipality of Coruche has decided to take action concerning the sustainability of its local charcoal industry. BEACON (Bridging European and Local Climate Action) brings together municipal decision-makers and environmental officers from Poland, Bulgaria, Romania, Greece, Germany, Portugal and the Czech Republic. In Portugal, it is coordinated by the Faculty of Sciences and the Institute of Social Sciences from Lisbon University. Municipalities are assessed in developing climate change mitigation projects and actions over the course of 3 years (2018-2021). Coruche, as one of 5 participating municipalities, works towards turning its charcoal industry more sustainable and reducing its environmental and health impacts. The technological obsolescence of Santana’s charcoal ovens represented a big potential to enhance their sustainability.

In a first step, an independent institute was engaged to measure the actual emissions of the charcoal industry. According to preliminary results, every day an estimated 30 tons of CO₂ are released into the atmosphere by the 321 ovens, amounting to 11 000 tons yearly. A significant occurrence of other gases hazardous to health, such as nitrogen oxide (Nox) and sulfur dioxide (SO₂), was also measured. The president, several municipal staff and a representative from the charcoal producers visited the most advanced Portuguese charcoal production unit, Carvão Zero near Oliveira de Azeméis. After several meetings between city administration and oven owners, the municipality acknowledged the high costs of adapting this modern technique and the reluctance of many carbon producers to update their operation since it entailed significant impacts to their livelihood. A collaborative and integrative decision-making process that also included technical professionals finally decided the upgrade of the existing charcoal ovens towards a type of retort kilns. This implies the much cheaper addition of a small high-heat combustion chamber to the existing ovens who would manage to eliminate all remaining toxic and polluting gases. Following the estimations, nearly all 11 000 tons of CO₂ could be retained. Additionally, the conversion efficiency would increase towards 466 kg of charcoal per 1000 kg of wood. It was calculated that the respective cost for these upgrades on the 321 ovens would be around 1 million Euros.

Despite the encouraging conversion prospects, the operational details have not been fixed, and the oven owners have yet to be informed in detail about how the change their ovens would undergo. Furthermore, the financing for this project is still not secured since currently there are no matching available funds that would allow the municipality to start the conversion of its charcoal industry.

51 million tons of charcoal are produced worldwide, most of it in Brazil, Asia, South-East Asia and Africa. Only 1 % is produced Europe, led by Poland, Ukraine and Spain. From those 51 million tons, only 2 million are actually exported, most charcoal is used domestically. In Europe, charcoal does not fall under the European Union Timber regulation, which is why in many EU countries the industries remain informal and opaque. Because of their significant environmental impacts, it is important to lead the charcoal industry towards sustainability, not only for Europe for the worldwide production. In this context, cases like Coruche awaken the hope that resource-scarce communities that are not mitigation forerunners can nevertheless become meaningful actors in the transition towards sustainability.

Alexandra Bussler, Phd Candidate and Research Assistant (BEACON) at ICS-ULisboa.