Ash recycling — A method to improve forest production or to restore acidified surface waters? Hans Ekvall a , Stefan Löfgren b , Göran Bostedt a,c, ⁎ a Dept. of Forest Economics, SLU, Umeå, Sweden b Dept. of Aquatic Sciences and Assessment, SLU, Uppsala, Sweden c Dept. of Economics, Umeå University, Umeå, Sweden abstract article info Article history: Received 10 January 2014 Received in revised form 17 March 2014 Accepted 22 April 2014 Available online xxxx Keywords: Ash recycling Acidification Forest growth Cost–benefit analysis This cost–benefit analysis compared different strategies for ash recycling in southern Swedish forests, with a spe- cial emphasis on the potential to use ash recycling as a measure to ameliorate acidification of soils and surface waters caused by acid deposition. Benefit transfer was used to estimate use values for sport fishing and non- use values in terms of existence values. The results show that the optimal share of acidified forest land that should be treated with ash depends on how optimistic one is about the effect of using ash to restore lakes and streams from acidification. More optimistic assumptions imply that the ash to larger extent should be used to ameliorate acidification. Using the most realistic assumption, given the experiences of forest liming, shows that acidified for- est land should not be treated with ash with the aim of restoring lakes and streams from acidification. From a so- cioeconomic point of view, ash simply does more good as fertilizer on forested organic soils. © 2014 Elsevier B.V. All rights reserved. 1. Introduction The increased demand for bioenergy has created a market for use of all part of the tree, where logging residues (tops and branches) are sold as biofuels. The supply of biofuels used for district heating has quadru- pled in Sweden since the 1990s of which wood fuels accounted for 32 TWh (46%) in 2010 (Swedish Energy Agency, 2011). Logging resi- dues (henceforth we will denote logging residues by the common Swedish acronym GROT) contributed with 7.3 TWh in 2007 (Swedish Forest Agency, 2008a). The large biomass removal causes an increased export of base cations (calcium, magnesium, potassium and sodium) and other nutrients bound to the plant tissues. The base cations origi- nate to a large extent from weathering of soils and if this process cannot balance the base cation removal by harvest, the soils are acidified (Iwald et al., 2012). To ameliorate this effect, ash generated at combustion of biofuels can be returned to the forest to complete the cycle. Besides base cations, ash recycling returns other important nutrients such as phosphorus, boron and copper, while nitrogen – limiting forest growth in most parts of Sweden (Egnell, 2011) – is lost during the combustion process. Based on 89 lime and ash application field experiments in Sweden, Finland and Norway, there are indications on that ash recycling may cause reduced forest production on less fertile soils and increased forest production on more productive soils. However, the variation is large and the relations are not statistically significant (Sikström et al., 2009). This is in agreement with earlier Swedish results (Jacobsson, 2003). In organic soils, nitrogen is rarely a limiting nutrient, while the availability of potassium and phosphorus may be restricted, reducing forest growth. Therefore, ash recycling can result in increased forest production, since the ash contains these elements (Silfverberg and Huikari, 1985). Currently, forest growth is estimated to contribute 30–70% of the acidification of Swedish forest soils (Swedish Environmental Protection Agency, 2007). At stand level and comparing whole-tree harvesting with maximum levels of current acid deposition the acidifying effect of harvesting Scots pine is 57–108%, Norway spruce 114–263% and birch 60–171%. The percentages are estimated from the ratio between net base cation uptake by the trees, which produces soil acidity, and the amounts of acid deposition (Iwald et al., 2012). Besides soil acidification, there is a growing concern in Sweden that the depletion in soil base cat- ion pools would also lead to surface water acidification associated with lower base cation concentrations in runoff (Swedish Environmental Protection Agency, 2007). For this reason the Swedish Forest Agency (2008b) recommends that for catchment areas of 300–2000 ha, the re- moval of logging residues from clear cuts and ash recycling should bal- ance each other over a 20 year period. The need for compensatory measures is also mentioned in the Swedish Forest Agency water policy (Swedish Forest Agency, 2010). It is assumed that ash recycling is extra motivated in southern Sweden due to the historically high acid deposi- tion, while nitrogen compensation may be more appropriate in northern Sweden. Forest Policy and Economics xxx (2014) xxx–xxx ⁎ Corresponding author at: Dept. of Forest Economics, SLU, S-901 83 Umeå, Sweden. Tel.: +46 90 786 5027. E-mail address: Goran.Bostedt@sekon.slu.se (G. Bostedt). FORPOL-01137; No of Pages 9 http://dx.doi.org/10.1016/j.forpol.2014.04.002 1389-9341/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Forest Policy and Economics journal homepage: www.elsevier.com/locate/forpol Please cite this article as: Ekvall, H., et al., Ash recycling — A method to improve forest production or to restore acidified surface waters? For. Policy Econ. (2014), http://dx.doi.org/10.1016/j.forpol.2014.04.002