Energy diversification, biomass heating is strategic
The military conflict between Russia and Ukraine has raised the question of diversification of energy supply sources with particular urgency. With this view, renewables are called upon to play a strategic role, as demonstrated by the story of the biomass district heating plant in the South Tyrolean municipality of Rasun-Anterselva, included as an example of good practicein the EU project "BRANCHES"
As was predictable from its very beginnings, the Russian invasion in Ukraine has gone far beyond the limits of the territories directly affected to involve the entire planet, not only emotionally. Given the complexity of the affair, we merely note how energy aspects continue to play a major role. This is not only by virtue of the pressure on supplies, but also because of the risks that infrastructures damaged by missiles or other offensive actions may generate. In this regard, one need only mention the sabotage of the Nord Stream pipeline - which used to transport a good 27.5 billion cubic metres per year of Russian gas to Europe over a distance of 1,220 km - which is now out of order and probably compromised forever. Another example of great concern concerns the Zaporizhzhia nuclear power plant (5.7 GW of power), the largest in Europe and among the first in the world, which is also on the brink of shutdown due to the attacks it has suffered and which raises fears of uncontrollable radiation. In this scenario, once again it is evident how strategic RES are. Indeed, these, in addition to not producing climate-changing gases or radioactive waste, have the enormous advantage of expressing themselves with scalable plants on a small scale and therefore distributed over the territory in large numbers, making them a war target of little interest due to damage in purely energetic terms or subsequent explosions and contamination. As is well known, thermal energy for domestic heating or industrial process heat is the predominant component of energy consumption in advanced societies. In this context, the convenience (environmental and social) of biomass district heating plants is of great topical interest. Today there is a widespread understanding of what district heating is and how it works. There are thousands of plants all over Europe and many have seen one - if not in person - at least in TV videos or on social media. There are also hundreds of studies, dissertations and technical reports that explore in detail the technical efficiency of various plant implementations, accurately assess their economic viability or quantify their local and global environmental benefits. So it would be of little use to add another description to the many that already exist, and which can easily be found in the bibliography. However, the plant in Rasun-Anterselva (Bolzano) - included as an example of good practice in the H2020 project "BRANCHES" acronym for Boosting RurAl Bioeconomy Networks following multi-actor approaCHES (www.branchesproject.eu) - can offer us the distinctive and very interesting element of its long history, which includes the concept of evolution. Today, Rasun can show us how it has been possible to respond to the continual succession of new challenges that in thirty years have punctuated the path of this plant, which is closely linked to its local setting. At the outset, in 1994, the thermal power plant and its heat distribution network were designed to serve the industrial area and the two residential hamlets of Niederrasen and Oberrasen, covering a total of more than 40 users, 5 of which were industrial. The capacity of the original plant was 5 MWt, supplied by two Kolbach boilers and distributed through a 12 km long network. Several reasons contributed to the decision to build the plant. On the one hand, the need to find a use for the large amount of wood waste produced both by a large local sawmill run by Johann Hellweger and by the adjacent panel factory; on the other hand, the rapid expansion of the hotel industry, which was interested in containing heating costs and reducing environmental impacts (traffic and emissions) due to the large fuel supplies. From these motivations, the choice was made that would prove to be a winner over the years. Thus, after a very successful start-up, the district heating network continued to expand, connecting new users until it was decided to upgrade the plant to enable it to operate in cogeneration mode with the additional production of electricity. Then, in 2008, a complete new cogeneration module was inaugurated, built around a 600 kW ORC turbine. The installation of a separate module was an intelligent technical solution, as this module could be sized to the heat demand of the summer period, so that it could be operated with maximum efficiency throughout the year. On the other hand, the original module would only be activated in the winter period, to meet the additional heat demand, with the benefit of never having to run either plant at partial power (which is very inefficient), and also of letting the old module "rest" during the summer, to allow it to save a little and make it last even longer, after 15 years of honourable service. Today, the Rasun plant serves almost 300 consumers through a 13 km network, producing 13.5 GWh of heat and 5 GWh of electricity annually, all of which is absolutely renewable. At present, it consumes 55,000 cubic metres of wood chips, most of which come from sawmills (50 per cent) and local forests (40 per cent). Indeed, the plant supports the management of the local forests through a 'political' price of €42 per cubic metre for the forestry waste material, which is a higher value than the current market price. In short, a complete success for the economy, the forests and the environment. Thus, the Rasun biomass power station has followed an evolutionary path to cope with the inevitable changes that have affected technology, the economy, the environment and society in thirty years. As far as the purely technological aspect is concerned, a virtuous path has been followed, guided by the development of new, more efficient and compact cogeneration plants that have made it possible to add the production of electricity to that of heating alone, with a very important economic benefit. Today, the production of electricity offers gains at least as important as those obtained from the sale of heat, and alone guarantees the economic sustainability of the plant. In this regard, one must also consider the impact of legislation that is subject to frequent adjustments, and often criticised for lacking a stable reference point that allows for long-term planning. Indeed, public support has changed several times in both duration and incentive shares, with adjustments generally going downwards. However, the reductions were proportionate to the steady increase in energy prices, so that the profitability of the plant remained unchanged. Such a compensation mechanism also made it possible to withstand the decrease in energy consumption: while climate warming and the increased energy efficiency of buildings led to a constant reduction in the energy sold to the individual user, the number of users grew continuously, and thus the overall amount of energy sold increased rather than decreased. Finally, a major concern has always been social acceptability: plans to build a new biomass plant often come up against opposition from residents and have a hard time gaining acceptance, when they still succeed. This was not the case in Rasun where, as early as 1992, the promoters of the plant had activated a broad participatory process. They even organised a trip to Austria for over 40 residents to demonstrate the economic and environmental benefits of wood-fired district heating. Today, it is clear to everyone that the Rasun plant offers competitively priced heating with a much higher environmental performance than the old individual heating systems. Many of these plants, replacing those based on the use of fossil fuels, can contribute to containing global warming and guaranteeing greater energy autonomy; problems that go back a long way and are now exacerbated by the continuing conflict between Russia and Ukraine.