Expertise

Charcoal: What are we barbecuing with?

Volker Haag, Gerald Koch | 2021

HF Institute of Wood Research

Scientists at the Thünen Centre of Competence on the Origin of Timber have examined the composition and declarations of around 450 charcoal and briquette assortments in recent years. With surprising results.

Das Bild zeigt glühende Holzbriketts in einer Grillschale.

Barbecuing with charcoal is the trend. According to figures from the Federal Statistical Office, consumption in Germany is more than 250,000 tons per year. However, most of the wood used does not come from "domestic forests". Around 85% of the charcoal sold in Germany is imported from abroad, often from tropical and subtropical regions, but also from Eastern European forests.

New microscopy method

Consumer and environmental protection organizations, as well as traders and importers, have asked the Thünen Competence Center several times since 2016 to examine commercial charcoal batches, such as those available in supermarkets, gas stations or DIY stores.

For the determination of the selected charcoal/briquette samples, a special 3D reflected-light microscopy technique is used to visualize the characteristic anatomical structural features. Compared to the microscopic determination of solid woods, flat (planar) sectional specimens cannot be produced from charcoal because the tissue is strongly decomposed by the charring process and is very brittle. Using the new digital microscopy technique, the uneven areas are digitally scanned and assembled within a programmable field. This initially produces a three-dimensional image, which is converted into a two-dimensional representation (Fig. 1).

Das zweigeteilte Bild zeigt links ein kleines Stück Holzkohle, das für die mikroskopische Untersuchung vorbereitet worden ist, und recht das Bild dieser Holzkohle, das vom 3-D-Auflichtmikroskop erzeugt wurde. — Fig. 1: Surface and microscopic image of a prepared charcoal sample scanned with a 3D reflected light microscope to determine the wood species.

The quality and sharpness of the images correspond to the results obtained "classically", i.e. in the preparation of microscopic thin sections. The high-resolution imaging makes it possible to detect the smallest cell structures and compare them with the structural features of more than 400 commercial tree species in the database of the Thünen Institute (Figs. 2 and 3). With the help of an integrated polarization technique, which makes the images appear optically green, the contrasts of the structural features can be further enhanced and native woods can be distinguished from tropical and subtropical species.

Das zweigeteilte Bild zeigt links die mikroskopischen Strukturmerkmale einer gescannten Oberfläche einer Holzkohleprobe, und rechts das mikroskopische Bild einer Querschnittaufnahme der Weißeiche. — Fig. 2: Comparison of the microscopic structural characteristics of a scanned surface of a charcoal sample (left) with a cross-sectional image of the wood species white oak (Quercus spp.) from the database of the Thünen Institute (right).

Das zweigeteilte Bild zeigt links die mikroskopischen Strukturmerkmale einer gescannten Holzkohleprobe der Holzart Manilkara zapota und recht s iner Holzkohleprobe, und rechts als Referenz das mikroskopische Bild eine Holzprobe der gleichen Art. — Fig. 3: Comparison of the microscopic structural characteristics of an analysed coal sample of the wood species Manilkara zapota from Mexico (left: scanned surface of the charcoal; right: reference photo from the database of the Thünen Institute)

High proportion of "critical" product ranges

An investigation of 20 charcoal assortments, commissioned by WWF in 2017, showed:

approx. 50% of the investigated assortments which were traded in Germany did not contain any information on the woods or tree species used,
only 30% of the traded charcoal and briquettes came from certified sources (FSC or PEFC),
about 40% of the assortments traded in Germany contained mainly woods from subtropical or tropical regions. Three quarters of these consisted exclusively of tropical/subtropical woods, and one quarter were admixtures of woods from temperate latitudes.

Further extensive test assignments followed. The examinations of around 450 assortments and approx. 6,750 microscopically analyzed individual samples have provided fundamental insights into the woods used as well as deviations from stated declarations.

In detail, it could be determined in 2019 that about 20% of the examined assortments must be evaluated as "critical" with regard to the stated declarations of the woods/tree species. These were essentially three case types:

Assortments that advertise the use of only certain wood species ("beech wood") and in which admixtures of other "native woods" were detected.
Assortments that do not contain any information about the woods used: These batches mostly consist entirely of tropical/subtropical woods.
Assortments with the declaration "from native hardwoods": Here, in addition to native woods such as beech, maple or oak, admixtures of tropical/subtropical woods could also be detected. In two cases, the batches were even FSC or PEFC certified.

In 2020, the Thünen Institute, in cooperation with WWF, conducted further investigations in a Europe-wide approach. For this, 150 charcoal batches from 11 European countries were analyzed. The results are summarized in the WWF brochure "Grillkohle 2020 – Eine EU-Marktanalyse" (in German).

Charcoal from tropical wood not in any case illegal

When evaluating these results, it must be borne in mind that the use of wood from subtropical or tropical regions for the production of charcoal cannot or should not be categorised as "illegal" or "overexploitation". In Namibia, for example, woods of the genus Acacia are processed into charcoal from land maintenance measures against bushes. In many tropical regions, thinnings or residual wood from the sawmill industry are used. However, in various countries, such as Paraguay or Nigeria, the local control possibilities are very limited.

In contrast to many other wood products, charcoal is not yet subject to the EU Timber Regulation (EUTR).

It must be clearly pointed out that an exact proof of origin with genetic methods or on the basis of the isotope technology, as it is used e.g. for sawn timber, is not possible with charcoal. Therefore, the proof of a legal use/processing of wood into charcoal can only be provided by microscopic examination of the assortments as well as careful labelling and complete certification. This is demanded by NGOs and already practiced by some manufacturers.

Facts & Figures

According to the Federal Statistical Office, around 215,000 tons of charcoal were imported into Germany in 2017. The most important supplying countries were Poland (79,000 t), Paraguay (32,000 t) and Ukraine (23,000 t). In 2015, 227,000 tons were imported, and the most important supplier country at that time was also Poland (74,000 t), followed by Paraguay (34,000 t) and Nigeria (32,000 t).

Charcoal from Poland, however, is not necessarily of Polish origin. Often, large batches of charcoal from other countries, such as African and South American, are blended there and put into sales packages. This makes traceability to the actual country of production difficult.

The FAO estimates global charcoal production at around 52 million tons per year. The main producing countries are (in descending order) Brazil, Nigeria, Ethiopia, India, DR Congo, Ghana, Tanzania, China, Madagascar, Thailand (as of 2015). More than 60% of charcoal is produced in Africa - mostly under unsustainable conditions.

The seals of FSC (Forest Stewardship Council) and PEFC (Programme for the Endorsement of Forest Certification Schemes) state that the wood for the charcoal comes from sustainable forest management. Even though false declarations have been uncovered in individual cases, these seals offer a high degree of security, especially since violations are punished by the organizations (e.g., with suspension of certification).

The DIN test seal (DIN EN 1860-2), on the other hand, does not make any statements about sustainability, but documents certain quality and health-related standards. It ensures, for example, that the charcoal does not contain any wood preservatives, slag, pitch or bitumen.

Charcoal is produced by heating wood in the absence of air and at temperatures of 200-300 °C. The by-products include wood tar and wood vinegar. According to the FAO, around half of all trees felled worldwide are processed into "fuelwood", i.e. energy wood (firewood, charcoal, biofuels, etc.). Charcoal is produced from 17% of the felled trees. Especially in emerging and developing countries, it is an important energy source used by the local population, e.g. for cooking.

As a rule, 5 to 10 tons of wood are needed to produce one ton of charcoal. With modern technology, however, it is possible to reduce consumption to 2.5 tons of wood per ton of charcoal.

Is barbecuing with a gas or electric appliance more climate-friendly than barbecuing with charcoal? A life cycle assessment study by TÜV Rheinland provides a surprising answer. According to the study, the type of barbecue is not nearly as important as the choice of food: Almost 95% of the climate-relevant emissions are caused by the barbecue food. Animal products such as beef and grilled cheese pollute the environment far more than vegetables over their entire life cycle. In a life cycle assessment, emissions and other environmental impacts are analyzed mathematically over the entire "life cycle" of a product.

For the analysis, the entire grilling process was considered, from the manufacture of the individual grills and the production of the grilled food to the grilling itself and the disposal of the grills.

As a service, the Thünen Centre of Competence in Hamburg offers the analysis of which woods were used for the production of charcoal. A special 3D reflected light microscopy technique is used for this purpose. A fee of € 336 plus VAT is charged per charcoal assortment.

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