Willows for Biomass Heating

UAB “Jūsų sodui” Pioneers the Propogation of Willow as a Source of Heat in Lithuania

Lithuania’s biomass potential. Although Lithuania’s oil and gas reserves are modest, it nevertheless has a substantial biomass potential. Approximately 500 000 ha of agricultural land (of a total of 3 million ha of arable land), which is not currently in use, could be turned over to cultivation of energy crops. It is true that this land could be utilized for afforestation purposes, but landowners should expect an economic return only 30-70 years after planting. By contrast, Swedish willow varieties (Salix viminalis), which are well-adapted to Lithuania’s climate, grow 8 times faster than conventional tree varieties. This means that a grower who establishes a willow plantation on his land could expect his first harvest of wood fuel within four years.   

Biomass district heating introduced in 1994. District heating suppliers began using wood residues (sawdust and woodchips left over from logging operations) in 1994, following the successful implementation of a Danish assistance program to utilize biomass in the town of Molėtai (100 km north of Vilnius). Other regional centers followed suit because switching to wood fuel was more economical than using heating oil or gas, even though global energy prices in the 1990s’ were low.

Since 2003, the rise in world oil and gas prices has spurred this process along so that by 2014, more than 40 percent of the output of local district heating plants was being generated by wood fuel. Such regional centers as Šilutė, Tauragė, Vilkaviškis, Marijampolė, Kazlų Rūda, Kelmė, Utena, Biržai, Ignalina, Švenčionys, Varėna and others presently obtain most of their district heating from wood fuel. In October 2006, Lithuania’s biomass heating capacity was increased substantially following the commissioning of a 60 MW furnace in Vilnius. Approximately 300 wood-fired heating furnaces  are presently in operation. 

Conventional wood fuel resources are limited. Plans envisage a three-fold increase in the use of biomass for district heating by 2020, but it is estimated that the existing forest area of Lithuania will produce sufficient wood resources for only a few more years of growth. Cultivating fast-growing willow on only a fraction of the unused farmland could easily yield enough wood fuel to eliminate anticipated shortfalls. Operators of municipally-owned district heating plants and those leased by the French Dalkia publicly endorse the idea of growing willow on unused farmland to expand available biomass resources for heating.

Properties of fast-growing willow.  The first harvest of willow stems generally takes place 4 years after planting. Once a mature root system has developed (after about 3 years), successive harvests occur every 3 years. A mature plantation will produce on average 20 tons of biomass each year. Thus, a harvest following 3 years of growth should yield roughly 60 tons of undried willow chips with a 50 percent humidity content. Once planted, willow trunks should maintain this rate of production 25-30 years. In the first two years of a plantation’s existence, biomass growth will be considerably less than 20 tons on account of weak root development.

Willow economics. As for heat values, we see that one ton of willow chips provides 9 GJ of energy, which is equivalent to the heat content of one ton of peat. A year’s growth of willow on one ha will yield 40 MWh of heat. Keeping a 10 MW heating plant operating for an entire heating season would required maintaining a willow plantation of 1 000-1 200 ha. A 10 MW district heating plant can heat the apartments of a town of approximately 12 000 inhabitants. Theoretically, planting 100 000 ha of willow plantations could be enough to supply 1 million inhabitants with centrally-distributed heat.

At present, heating plant operators are paying 17 EUR per 1 MWh of heat energy, which means that one ha should provide the equivalent of 680 EUR of wood fuel each year. For his part, the grower should earn a profit of 340 EUR annually from each ha, following deductions for cultivation costs, the expense of harvesting willow chips and selling the fuel through intermediaries.

Planting material for one ha costs about 520 EUR (assuming a planting density of 15 000 units per ha), while the estimated maintenance expenses for the first two years totals 400 EUR. Maintenance costs after the first two years are much smaller.

How to maintain a willow plantation. The single most important factor in ensuring a productive plantation is effective weed control. During the first two years of cultivation, willow plantings are unable to compete successfully with weeds. If weeds establish themselves on more than 20 percent of the surface of a plantation, the result could be stunted plants and a reduced yield of as much as 50 percent. After planting, the field should be cultivated three-four times the first year and at least two times during the second year of a plantation’s growth. By the third year, the willows’ root system will be strong enough to guarantee a stem height of about 4 meters, which will obviate the need for further weed removal. The stems will block out sunlight to the soil surface area, and thus prevent the weeds from thriving. No more weed control will be necessary during the remaining 23-28 years of a plantation’s useful life.

Harvesting willow chips. In Sweden harvesting willow stems is accomplished by using specially modified corn harvesters (generally Claas Jaguars), which simultaneously cut the willows and shred them into chips. The chips are initially carried in a bin attached to the harvester, and then transferred to trucks for immediate delivery to hating plants. One Claas Jaguar can harvest one ha in 1,5 hours. This harvester’s yearly capacity is about 1 000 ha. About 15 harvesters are in continuous use in Sweden during the long heating season, taking in the harvest from 15 000 ha of willow plantations. The cost of purchasing a new Claas Jaguar harvester is 300 000 EUR.

Jūsų sodui propogates the idea of using willow to produce residential heat in Lithuania.
Jūsų sodui cooperates with SalixEnergi Europa AB in marketing Swedish willow varieties locally. Over the past four years we have been developing local interest in growing willow for heat energy production. We have an 8 hectare willow plantation which produces willow cuttings for planting. We also have purchased a four-row step planter, which has planted an area of 800 ha. Counting other willow varieties imported into Lithuania, we believe that a total of 2000 ha of fast growing willows have been planted in Lithuania since 2003.

Jūsų sodui has presented the ecological and economic benefits of willow to Lithuanian officialdom, experts and the general public. We have helped produce many television and radio segments about the cultivation and use of willow. We have written articles for publication in local newspapers and magazines. We provide free consultation services to persons interested in establishing willow plantations. Besides Jūsų sodui, the Lithuanian Biomass Association, has also participated in propagating willow growing.