Research of short rotation wood energy crops in Latvia

Approximately 56 % of Latvia territory is covered by forests, why forestry and logging as well an export of wood chips and pellets are very important in country total export balance. As a result of the decrease in agricultural production, approximately 1,5 mill. ha of agricultural lands in Latvia are not used any more for food production, and these areas have been left to neglect for the last 20 years. It describes because establishing of plantations of short rotation woody coppice was not very popular and this business are still in initial stage. Since this year woody short rotation coppice (willows, aspens and gey alder coppice with 5 year rotation cycle) are included in total scheme of direct payments for management of agricultural lands (Rules of cabinet of ministers Nr.269 Procedures by which State and European Union Support is Granted to Agriculture in the Framework of Direct Support Schemes ).

Topical issues become not only the production of solid biofuel, but also the utilization of organic wastes, including waste water sludge some of technologies how to use waste for energy production and fertilizing of plantations are popularized during implementation of the project  "Elaboration of eco-effective standard documentation package for implementation of waste water sludge treatment technologies in Latvia" (http://www.lasa.lv/EEA/Eng_index.php).

The aim of the research studies done at Latvia State Forest Research institute “Silava” is to solve both of these problems simultaneously by using waste water sludge as a fertilizer in short rotation willow plantations, thus increasing the productivity of the plantations, results of research are described and analysed at project reports and summaries which are available for download on research institute web site (http://www.silava.lv/mainen/aboutus.aspx).

There has been an attempt to elaborate an ecologically based model for the utilization of waste water sludge in short rotation willow plantations by estimated the productivity of the plantations in different soils and under different growing conditions, through the evaluation of environmental effects of the sludge applications, and by providing solutions for environmentally-safe utilization of the sludge, results are used for working out of promotion paper - dissertation “Using of waste water sludge in short rotation willow coppice” (http://llufb.llu.lv/dissertation-summary/forest/Dagnija_Lazdina_promocijas-darba-kopsavilkums-2009-LLU-MF.pdf ).

The first experimental plantations were established just from 2004 to 2006. Clones of willows originated in Sweden (Tora, Torhild, Sven) were used in the experiment and one promising variety of Salix burjatica. The productivity of different clones, using waste water sludge as a fertilizer, and changes in soil properties were evaluated at the Olaine nursery (Figure 1).

Figure 1 First winter and early autumn harvest of willows like on commercial plantations at experimental trials at Olaine nursery.

If waste water sludge is used in willow plantations, a dose of 10tdryha^-1 can be applied once every 5 years (corresponding to the maximum permissible 2 tdryha^-1 annually).

Productivity measures are estimated – varieties Tora and Torhild, which are recognized within the scope of this study as the most promising for Latvian conditions, during a 3-year rotation cycle produce 28 - 31 tdry ha^-1.