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Prof. Volker Quaschning, HTW University of Applied Sciences Berlin

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DW: It sounds really great - fast-growing trees which can be used for sustainable energy. Is that the key solution for our energy problems of the future?

Volker Quaschning: Germany wants to go to 100 percent renewables and for that way the biomass production is very important. We see 10-15 percent or even 20 that we can cover here with biomass, and for that we have to look at what type of biomass we are using for that. We can use, for example, corn and produce biofuels for car driving. That is a big discussion because for that we need a lot of fertilizers.

And of course we're in a certain competition with a food plant, which has driven the prices. for example, in Mexico we've had that quite extreme, so no problems with trees anymore. Is that right?

Yes, that is the most interesting point, so from the ethical point of view, these plants are very good so we have no competition here for food production and it is a very sustainable way of growing plants here in the sector.

And what kind of potential do you see in Germany. We have lots of forest here already.

Yes, we have forest, but if we are using all biomass we can collect here during the year, we see we can cover around 15 percent with biomass from the total energy demand. And these plants here, they can only cover a part of the biomass sector. So we see mainly 1, 2, or 3 percent they can cover from the total energy demand - but it is an important part, that we can use.

As you just said there is a big problem with the fertilizers with usual biomass plants like corn or rapeseed, for example, which has ruined the eco-balance. Is there a chance to actually improve that, or should we just forget about corn and rapeseed and just grow fast-growing trees?

From my point of view we should do both with the plants. We can use the plants for food production - the corn itself - and we can use the residues of the plants here and produce energy from the residues. This is a good idea to do that, so we need the plants for food production, the residues for energy production, and then we can do it in a sustainable way.

But the technology for just using the residues is not really working well so far.

It is expensive. The technology works, we know what to do but it cannot compete here at the moment with fuel oil, with the conventional crude oil. That we have to solve, but if we have a solution for that, it is a good way we can go.

What about the energy you can actually harvest from trees or from biomass?

We can collect efficiency. About 1/2 percent of the incoming solar energy is collected here and converted to biomass energy, and if you compare it to photovoltaics, for example, modern solar cells reach about 20 percent efficiency. So the efficiency of the plants is much lower than the efficiency of, for example, solar cells.

That is very low actually. Can we still save the climate with these trees or with biomass?

I think we need it because the storage is already included in the plants. And this is the advantage compared to photovoltaics. So if you have solar electricity, we have to use it at the same time when the sun is shining or we need a storage. Biomass we can harvest here - it grows during summertime and we can use the biomass energy during winter, and this is a big advantage we have here in the biomass sector.

So biomass could come up to about 15 to 20 percent of our energy needs. What about the rest? Where does it come from?

The efficiency of solar energy or solar cells is much higher so we see the highest potential in Germany for wind and solar energy. If we combine all technologies, your solar energy, wind energy and biomass we can come to 100 percent renewables.

Interview: Ingolf Baur