2nd RCN Conference on Pan American Biofuels & Bioenergy Sustainability
Dendroenergy: short-rotation forestry considerations in Argentina
In order to have an overview regarding silvicultural models potentially applicable in Argentina, the ranges of expected productivity and environmental viability, was formed a interagency working group involving researchers from CONICET, professionals MAGyP, and technical 13 units of INTA.
These dendroenergy plantations are aimed at obtaining high amounts of biomass without special quality requirements and through short-term rotations. At this point, decisions like selection of fast-growing species with regrowth capacity and management system that support high densities converge. Being low-priced products, in comparative terms, it is also required to minimize production costs, and minimize the cost of transport to basins.
Argentina is a large territorial country which hosts a wide variety of natural and productive environments. In this diversity, forestry develops in regions of very diverse biophysical and socioeconomic features, sometimes contrasting.
In this context, in order to determine the eligible areas at regional or landscape-scale, criteria based on productivity aspects and restrictions associated with environmental care were used. Legal safeguards from different jurisdictional order were the first discriminatory elements considered. This included land-use planning from Native Forest Law. The second exclusion criterion referred to water availability, where ineligible regions were those where rainfall/year was less than 800 mm and water balance was negative (arid, semi-arid and sub-humid). Based upon this analysis, six regions with potential production of biomass for energy purpose were identified: Mesopotamia, Pampas, Central, Northwest, Delta, and Patagonia Andina.
Considering the little information available, silvicultural proposals were based on knowledge that emerged from commercial plantations for quality timber production or pulp industry. Few high density biomass production records were available for some species and areas.
The species identified as feasible correspond to Eucalyptus genders, Salicáceas clones, Pinus species, and a native species (Nothofagus antartica, ñire). Different species of eucalypts are proposed as eligible in 5 out of the 6 regions, Salicáceas clones in 3, and Pinus species in 2 of them. The usage of materials such as Eucalyptus, Salix and Populus is preferred since they have the advantage of being managed by regrowth.
Different silvicultural schemes for different regions were generated. On this basis it was possible to estimate the expected production rates of biomass as a function of the genetic material, site quality, initial density, rotation period and, as for Delta, the structural measures implemented for water management.
Wood energy plantations, inherently represent a model of highly vulnerable sink and source- to current invasive pests and diseases affecting pines, eucalyptus and salicáceas in Argentina. It is important to note, then, that in established crops intended for forestation near traditional forest production can pose serious health and economic risks. Consequently, you should consider susceptibility to pests / diseases affecting the species to use, and at the same time imposes establish a monitoring program to anticipate potential impacts.
Because of the aforementioned characteristics, the wood energy plantations set up an intensive model of land use and landscape. Thus, the main expected impacts on resources and environmental services were identified and proposals were elaborated to encourage that its implementation takes place in a framework of environmental and productive sustainability.
The expected impacts on soil quality result in the intensification of the processes of erosion, loss of organic matter and nutrients, compactation, and secondary salinization. It is also expected that plantations are located on low quality soils - lower value, less competition with other uses - usually characterized for being fragile soils, marginal in terms of soil fertility, and therefore very sensitive to degradation processes. Due to this consideration, a precautionary attitude prevails in the planning process, site selection, and management modalities to be implemented.
Being fast growing species, handled at high density, water consumption at micro-basin level may be critical if the proportion allocated to this type of plantations is not suitably determined; especially in regions with water balance close to neutral or in basins that supply water to cities or to rural people.
In terms of impacts on biodiversity, management based on high densities generates strong limitations for solar energy access and thus minimizes internal biodiversity of the stand. This process can lead to greater limitations as long as planted acreage increases and the location of the stands is not properly planned in the landscape.
It is emphasized that the environmental viability of projects based on wood energy plantations increases as long as its planning and implementation consider a precautionary attitude towards environmental care, to address aspects of conservation of the resources mentioned above, which stands at landscape level implemented with a pattern of scattered distribution, small size, and they are scheduled to meet local energy demands.
Notwithstanding what has already been considered, it is compulsory to consider that the conservation of the soil, the biodiversity and the quality and quantity of water are basic sustainability paradigms, essential for the maintenance of environmental services, and thus to meet the basic needs of societies.
In this context, the relationship energy crops - environmental impact - sustainability is a central theme in the international debate on bioenergy; because if the intensification in land use can trigger degradation processes, one may wonder up to what extent the income, and / or volume of fossil fuel avoided, outweigh the "hidden" environmental costs, and the expected risk of increasing soil area abandoned due to low capacity of production of goods and services, including food production.