|Sysav WtE Plant|
Technically speaking, what can we expect from the technology in terms of improvements?
The big technical challenges with the present technology are today three and where we will improve:
– to reduce and minimize the amount of bottom ash. After the waste-to-energy process there still is about 20% of bottom ash as a residue. That means that there still is too much of unburnable waste coming to the waste-to-energy plants. We have to significantly reduce that amount to be more efficient in recovering energy and minimize the environmental problems of the residues.
– to develop a safe and environmentally correct way of final handling of the flue gas cleaning residues and to recover as much as technical and economically possible of the metal content in these residues and in the bottom ash
– to increase the electrical efficiency in the waste-to-energy plants. With high prices for electricity the power production should increase. Based upon some successful cases from some new European waste-to-energy plants. I would not hesitate to increase the steam figures above 400 degrees and 40 bars when building a new plant.
Last but not least, in a recent discussion I heard, probably for the 100th time in last two years, that incineration is dead and that gasification and plasma pyrolysis will soon substitute all incineration plants. What is the current status of those technologies? Are they applicable for Mixed MSW? Are there commercial applications and operational experiences? After all, is it something we can trust?
|Sysav WtE Plant|
A number of plants were built in Europe and a number of efforts were done to successfully scale up the technology. However, it didn´t work anywhere unless you had a very very homogenous input of fuel to the reactors. Waste is not a homogenous fuel. It has so far turned out to be too heterogenous to be able to treat in a gasification or pyrolysis process, irrespective of how you pre-treat the waste. It is absolutely not applicable for mixed MSW with today’s technology. Another very negative factor is that the energy balance very often has turned out to be negative.
It would, from an environmentally point of view, be an excellent method if it worked, with low emissions and with a very small and environmentally safe residue, but unfortunately the situation today and the experiences are the same today as almost 40 years ago, even if there have been and still are efforts to introduce gasification and pyrolysis on the market.
When planning for the two new furnaces in the Sysav-plant there were proposals and some efforts that we should change from conventional grate incineration to gasification. I said absolutely “No”, but to be fair to those who believed that gasification was the best technology we decided to carry out a study and a comparison between the two technologies. The answer was very clear: gasification would result in a negative energy balance. I am happy to say that we made the right decision, our results and experiences from the grate technology gives the answer.
I absolutely don´t want to be negative, it would be fantastic if the gasification and pyrolysis technology will develop in such a way that you can use it for MSW , with a clear positive energy balance and working in a safe way for those working at the plant.
I remember when I as a young person in the waste business, full of belief in new methods and technologies, in the middle 1970-ies participated in a very good conference in Antwerp about waste management. There was a whole session about gasification and pyrolysis and I was full of enthusiasm, expecting a lot from the different presentations. On the way in to the conference room I walked beside an older gentleman and colleague from Germany. I told him about my expectations and he looked very friendly upon me telling me that he had started to work with R&D within waste management already in 1922 at the Batelle Institute in Frankfurt, and the task was to gasify/pyrolyse waste in a better way than could be done in a waste incineration plant. He told me that they without any success had been trying to do so and that he still had very little faith gasification/pyrolysis could be developed and turn out to be a successful technology for waste.
I was of course very disappointed to hear this, but still believed it was the technology for the future handling of waste. The bad experiences coming up very soon after that conference and all the failures and unsuccessful efforts since then has made me very skeptical.
Unfortunately, I believe there is a long way still to go, but we shouldn´t give up our efforts.”