Biorefinery – Est-For Invest

Technology and best available technology

Est-For Invest`s consultant, Head of Hendrikson & Ko Environmental Management Department, Juhan Ruut, explains what kind of technology the planned biorefinery intends to use and what best available technology means. 

Several questions have been raised in the media in connection with the biorefinery – what is the planned technology, is it the best it can be, meanwhile trying to interpret the application of the best available technology. Parallels are drawn with Äänekoski biorefinery in Finland. How adequate are these comparisons?

What do we know at this point? In the biorefinery, the wood raw material is processed into different components like cellulose, hemicellulose, lignin and additives, which can be processed into different bioproducts in the future. Cellulose is obtained by sulfate cooking process i.e. kraft technology. The maximum production capacity is 2700 tonnes of cellulose and other bioproducts a day, on average 750 000 tonnes a tear. Considering the 18-month maintenance interval and ratios of different types of wood, the total production capacity in different years may vary from 650 000 to 750 000 tonnes and after finetuning the refinery`s production processes, may reach 800 000 tonnes a year in the future. There are no plans to start producing paper from the cellulose as the intention is to retain the possibility to produce more innovative bioproducts in the future.

The by-products of the manufacturing process are tall oil and green energy, including electricity. In the framework of the biorefinery, a combined heat and power facility will be established, with rated wattage of about 180 MW. On average, about 30% of generated power is sold to the grid. A biorefinery has great energy efficiency – the plant covers its own energy demand, and the surplus heat is used to generate green power.

The raw materials the biorefinery would use are birch, pine and spruce pulpwood and wood chips produced in sawmills. The raw material demand is ca 3.3 million m3 of roundwood and wood chips a year. The ratio of coniferous wood and non-coniferous wood is not strictly 2/3 and 1/3 – this is an indicative ratio serving as the basis for initial calculations. The actual ratio between different types of wood depends on the refinery`s product portfolio and availability of raw material, i.e. future period`s silviculture and logging policy – if there is a shortage of coniferous wood, then more birch will be processed.

Demand for other resources:

  • land – the refinery`s territory would be ca 100 ha, the need for land under infrastructure will be identified during the planning process and depends on the specific location`s distance from the river and railway and also other applied technologies;
  • in addition to wood, the refinery`s work process requires surface water up to 30 m3 for finished production tonne i.e. up to 25.5 million m3/y, drawn from the River Emajõgi, which makes up approximately 1.3% of the average Emajõgi flow (approximately the same volume of thoroughly treated waste water is directed back into the river);
  • in the process of chemical cellulose production, sodium sulfate and lime are added to the pulp, in bleaching, chlorine dioxide is presumably used – the chemicals circulate in a closed cycle to the extent of 80–90%, 50–60 kg chemical additives are used per tonne of output;
  • the refinery`s work process uses power and heat which the plant produces itself.

The water drawn from Emajõgi will be directed back to the river as treated waste water after it has gone through the process – 25–30 m3 of water per 1 tonne of finished product i.e. 21.25–25.5 million m3/y. Cooling towers will be used, so the cooling water will not be discharged to the environment. A certain amount of heat will be released to the environment with the waste water, but according to initial calculations, the increase of the river water temperature at the place the pipeline discharges into the river is 0.3 degrees on average, even less further away.

The refinery`s operations will also involve emission of substances into the aquatic environment and ambient air, the amounts will be specified during further technological design and environmental impact assessment, but the levels must correspond to best available technology (BAT) requirements and ensure quality of living environment. The sewage sludge and ash from the biorefinery will preferably be treated as by-products. The amounts primarily depend on the method chosen for sewage sludge treatment: for example, if the optimal alternative would be utilisation in the refinery to generate energy, then sludge will not form, but the ash volumes will grow.

What else does the planned technology depend on?

A biorefinery differs from a conventional pulp mill in obtaining other products in addition to cellulose. This also presumes changes compared to conventional pulping process. Currently, the exact product portfolio`s development and coordination with the project`s potential financers is underway. Accompanying products, including by-products, can only be produced if there is a market for them and suitable cooperation partners are found for marketing.

In addition to pulp, the refinery`s product portfolio will include dissolving pulp. This means that the manufacturing process must include a stage where the hemicellulose in the wood is separated with hydrolysis before cooking the pulp.

How will the impact assessment influence the planned refinery?

In the initial, more general stages, the focus will be on strategically significant issues and alternative development scenarios will be assessed. In this stage, it is enough to know what the main concept of utilised technology will be. Economic and socio-cultural impact assessment is very important, including ascertaining social expectations for the location and operation of the biorefinery by explaining different development scenarios; the process should also provide information on what is the acceptable technological design threshold. For example, odour: according to environmental permits, Finnish Metsä group`s Äänekoski bioproduct mill`s so-called odour-proof level is 95 per cent (the new mill was built to replace an existing mill), In the Finnish city of Kuopio, in FinnPulp mill`s integrated permit, it is 98 per cent (new mill next to the university town). The plan is to design the Est-For mill with a triple collection and disposal system for unpleasant odour, which guarantees that 99 per cent of the time, there is no emission of smell. After the location has been decided, assessment of the project with the level of detail of environmental impact will take place.

During this process, different alternatives will be considered, which involves comparative assessment of impacts. In my experience as a leading expert, there are usually three: first, the option preferred by the developer, then the option that the mill will not be built and if necessary, the option will be included in the assessment where the volume of the planned activities is restricted or a different technology is utilised to mitigate the significant environmental impact that may be involved.

The final technological solution for the mill that an integrated environmental permit will be applied for, depends on the outcomes of the impact assessment process – input is given to draw up the technical project, i.e. if necessary, the previously submitted project is corrected and specified in conformity with the additional restrictions that emerged from the environmental impact assessment process.

Building a new mill cannot mimic any existing mill – a significant part of the environmental permit derives from the environmental conditions in the exact location. Also, the national legislative differences must be followed. In water sector, Estonian legislation is much stricter than EU directives. Over time BAT requirements are reviewed and after new requirements are adopted, the built mills have four years to apply the new requirements. Therefore, it is not appropriate to assume that the developer will automatically choose the cheapest solution according to the valid BAT or copy the solution from somewhere else.