Bioethanol from old baked goods

Bioethanol from old baked goods

Stale bread could become an environmentally friendly fuel in the future. © Slimoche/ iStock

In Germany, around 600,000 tons of baked goods are overproduced every year. Although some loaves of bread and rolls are still used in the form of animal feed or wood chips, many old baked goods end up in the trash. This should now come to an end: A new pilot project aims to produce the sustainable fuel bioethanol from stale bread and rolls. If the method prevails, 162 million liters of bioethanol could be produced annually from excess pastry.

Around eleven million tons of food end up in the trash in Germany every year. Baked goods such as bread, rolls and Danish pastries are also affected by this food waste. According to estimates, German bakeries produce a surplus of 600,000 tons of goods every year. Some of these old baked goods are given a second life: as animal feed, wood chips or in biogas plants. But bread recycling is complex and expensive, which is why a lot of old baked goods still end up in the trash.

Two birds with one stone

However, that could soon change – at least if the initiators of the “The Bread Distillery” project have their way. The idea: produce bioethanol from old bread, baguettes and cakes – an environmentally friendly fuel alternative to petrol. At German gas stations, for example, bioethanol is contained in fuel called “Super E10”. Anyone who fills up at a pump declared in this way receives a mixture of 90 percent regular gasoline and up to ten percent bioethanol. Bioethanol is currently produced primarily from agricultural crops such as corn, wheat and sugar cane. But the more the production of alternative fuels increases, the more these plants compete with the cultivation of food in terms of area.

Producing bioethanol from old baked goods would kill two birds with one stone. This is exactly what Germany’s first “bread distillery” is trying to do, which opened a few days ago in Friedrichshafen. However, it was a long way from getting there. First of all, it had to be clarified whether bread could actually be fermented and thus used as an alcohol-containing basis for bioethanol production. The prerequisites for this would actually be met: “Bread contains significant amounts of starch. It is easily broken down by special enzymes into sugar molecules, which the yeast then converts into alcohol,” explains Daniel Einfalt from the research and teaching distillery at the University of Hohenheim.

Pilot plant
The pilot plant © Lukas Müller

Pastries become ethanol

In practice, however, it is not the bread with the highest starch content – white bread – that achieves the best results, as the tests showed. In fact, white bread lagged significantly behind other baked goods such as rolls, pretzels, rye bread or cream cakes. “We attribute this to the low protein content of white bread,” says Einfalt. “Because the protein building blocks are essential for the activity of the yeast.” However, if special fermentation salts are specifically added to the old baked goods, which supply the yeast with nitrogen and phosphate, the fermentation time is shortened and the ethanol yield increases.

The bread distillery in Friedrichshafen is still a pilot project, but it shouldn’t stay that way. The initiators hope to be able to attract as many imitators as possible across Germany to the idea. Once the method is used across the board, it could produce 162 million liters of bioethanol annually from old baked goods. Bread distilleries would not only make a major contribution to recycling, but would also earn good money. The project managers estimate that medium-sized companies could make around five million euros in additional sales per year by recycling their old baked goods.

In the long term, not only the ethanol obtained, but also the distillation residue could be used. Due to its high protein content, it is suitable as animal feed, for example, but there are still legal hurdles. The same applies to the approach of using ethanol to produce aromatic spirits in addition to producing fuel. Such bread schnapps is currently still failing due to EU law.

Source: University of Hohenheim

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