This article represents the results of the research project 'Forest energy from small-dimension stands, infra-structure objects and stumps' realized in cooperation between Joint stock company Latvijas valsts meži (Latvia's state forests), SKOGFORSK (The Forestry Research Institute of Sweden) and Latvian State Forestry Research Institute Silava. The article is covering issues related to the results of stump harvesting field study realized in November, 2008. A scope of the study was to estimate costs of stump harvesting and to evaluate working methods and influencing factors related to extraction of stumps. Better harvesting conditions (flat landscape and lack of stones in soil) led to increased productivity of stump extraction in Latvian trials (5.2 tdry (tdry - tons of dry mass) of stumps per effective hour (E0-h)) in comparison to average figures in Scandinavian studies. Load sizes of the forwarder ranged from 5.5 to 9.3 t which is about half of the maximum load of forwarder. Average productivity of forwarding was 6.3 tdry E0-hE-1. Productivity of stump transport (distance - 7 km) was 3.5 tdry E0-hE-1. Productivity of comminution was 10 tdry E0-hE-1. Prime cost of the stump harvesting, including extraction, forwarding, stump transport (7 km one direction), comminution and chip transport (50 km one direction) was 6.3 LVL LVmE-3 (LV - loose volume). 'Environmental footprint' of the stump harvesting in terms of carbon (C) emissions was 2.5 kg C LVmE-3 of wood chips at terminal. Stumps demonstrated considerably higher heat value (5.7 MWh tdryE-1 against 4.7 MWh tdryE-1 for the hog fuel from a slash).

Performing biofuel use studies, a large number of parameters that characterize engine operation under different conditions and with different fuel mixtures have to be identified. The real driving conditions are usually simulated by driving cycles on a laboratory chassis dynamometer. There are two major categories of driving cycles: legislative and non-legislative. From the viewpoint of cycle formation there are also two ways. One is composed of various driving modes of constant acceleration, deceleration and speed, and is referred to as modal or polygonal. The other type is derived from actual driving data and is called as 'real world' cycle. There is a strong agreement among researchers that driving characteristics of each city are unique because of different vehicle fleet composition, driving behaviour and road network topography. It is therefore better to develop own driving cycles than using driving cycles developed elsewhere. The aim of this investigation is to develop driving cycles or models for dynamometer control software corresponding to peculiarities of Latvia. The procedure for cycle development and fuel consumption and exhaust emissions measurement was worked out. Using real driving data on the Jelgava streets, models simulating driving in different urban areas were constructed. The model quality was determined using vehicle driving parameters and fuel consumption measurement results from both the road and laboratory tests. Since the obtained data coincidence of all the parameters exceeded 98%, the elaborated cycles can be used for the biofuel use efficiency determination.

This article is covering results of pre-commercial thinning, forest infrastructure and undergrowth harvesting field studies implemented in July, 2007 by Skogforsk and LSFRI Silava. A scope of the study was to estimate prime costs of biofuel production from small trees and to compare two types of harvester heads (Bracke C16.a and Ponsse EH25). The productivity in pre-commercial thinning expressed as trees per E0-h (effective hour) ranged between 53 (Ponsse) and 118 (Bracke) in the pine stand and 150 (Bracke) in the mixed spruce stand. In comparison the LVm3 (LV - loose volume) ranged between 9.9 (Ponsse) and 14.1 (Bracke) in the pine stand and was 13.0 (Bracke) in the mixed spruce stand. In the forest infrastructure (roadside ditches) harvesting productivity was 8.2 LVm3 E0-hE-1 for Ponsse and 12.5 LVm3 E0-hE-1 for Bracke. Productivity was economically insufficient in undergrowth removal, both in harvesting (Bracke) and forwarding (Ponsse) operations, respectively 1.1 and 2.6 LVm3 E0-hE-1. Prime costs of harvesting, forwarding, comminution and chip transport (50 km one direction) in pre-commercial thinning in calculation to LVL LVm-3 were 5.93 for Ponsse and 5.85 for Bracke. Prime costs in forest infrastructure in LVL LVmE-3 were 4.97 (Ponsse) and 6.36 (Bracke). Only Bracke was tested in the undergrowth, where prime costs were 37.55 LVL LVm-3. 'Environmental footprint' of biofuel production from small trees in terms of carbon (C) emissions ranged from 2.6 to 10.2 kg CLVmE-3, including road transport (50 km) to terminal.

Rising oil prices, national security concerns, the desire to increase farm incomes, and a host of new and improved technologies are propelling the European Union to set the directive for the year 2010 – each member state should achieve at least 5.75% biofuel usage of all used transport fuel. The report on the progress made in the use of renewable fuels shows that the average Member State of the EU has achieved only 52% of its target, and biofuels’ share in 2010 will not raise much above 4%. The prices of different biofuels are still not able to compete with oil based fuel prices. One of the possible ways how to solve this problem is to optimize biofuel supply chains using different methods of systems engineering. The aims of this investigation were finding out appropriate simulation tools for biofuel supply chain modelling, development of rapeseed oil supply chains for different production types, and modelling the developed supply chains. As the result of software survey, two packages were chosen – AnyLogic and ExtendSim Suite. Modelling studies showed that rapeseed oil supply chain is very sensitive, because changing just single parameters in a short scale, the actual cost price of 1 litre of oil changes considerably. Comparing the fossil diesel fuel prices with rape oil actual cost from modelling studies, the use of oil as a fuel for farm machinery seems to be profitable. Analysis of costs distribution shows that the greatest part is composed by rapeseed growing expenses.

Grain after enzymatic treatment, which is a starch-containing raw material, is used for ethanol production. Bioethanol production in Latvia began in 2006. Extraction of biofuels is a clean process, because the byproduct is used in various sectors of the economy. The bioethanol in Latvia was derived primarily from winter wheat, winter rye, and winter triticale. The objective of the research is to determine the different nitrogen fertiliser rates required for winter cereal crop yields and bioethanol outcome. The trials were carried out from 2005 to 2008 in Agricultural Science Centre of Latgale (Latvia). The method (ethanol outcome) is based on fermentation of saccharified cereal samples by yeast Saccharomyces cerevisiae followed by the calculation of ethanol outcome and speed of fermentation. The highest starch content was in winter wheat and winter triticale grain, but the lowest - in winter rye grains. A close negative correlation (p is less than 0.05) was found for winter triticale and winter wheat between the ethanol outcome and thousand grain weight. Production of bioethanol from rye starch content is used with full utilisation of grain. The winter wheat has the largest ethanol outcome from one hectare.

One of the primary reasons for expanding the production and use of biofuels is the potential environmental benefit that can be obtained from replacing fossil fuels with fuels derived from renewable biomass resources. This investigation examines the impact of biofuels on the environment directly from the practical view point analysing how the internal combustion engine emission concentration changes using the most common first-generation biofuels in Latvia – biodiesel, rapeseed oil and bioethanol. Laboratory experiments were performed on a chassis dynamometer Mustang MD1750, but the content of exhaust gases components was determined by the AV L SESAM FTIR measurement system. Investigation shows that the trends of different exhaust gas component changes, which would be the same for all investigated fuels, don't exist, i.e., each vehicle and biofuel type or blend is particular and has to be analysed separately. In comparison with fossil diesel, running the car VW Golf on rapeseed oil the average reduction of NOx was 10%, but SO2 – 59%. The CO, CO2, unburned hydrocarbon and mechanical particle emissions were higher. Running the car Opel Vectra on biodiesel the amount of NOx in comparison with fossil diesel increased in average by about 12%, the amount of mechanical particles and unburned hydrocarbons decreased quite significantly, but just a small increase of CO and SO2 was observed. Testing the car VW Passat on gasoline-bioethanol blends increase of the bioethanol content in the fuel blend increased also the NOx content in exhaust gases, but the content of CO, CO2 and NH3 decreased.

The utilization of traditional fossil fuels (oil, gas) as primary energy resources causes a destabilization of the eco-environmental situation in the world. Latvia has to significantly decrease energy imports from its neighbouring countries. This can be achieved by using high-quality local primary renewable energy sources. One of the solutions is to utilize anaerobic fermentation for biogas production. This process can be ensured by utilizing manure, food waste as well as energy biomass - wood, grass and maize. Biogas is utilized as a primary energy source in a cogeneration plant which is a combined cycle plant for electricity and heat power production. Microcogeneration plant for farming household needs would ensure an independent power supply, in case the overall electrical network is in a state of emergency. In order to ensure optimal biogas yield, which, in turn, would ensure a stable operation of the microcogeneration plant, it is important to know the parameters and quality of the biomass that have been filled in bioreactor. This research deals with the influence of the linkage biomass type on the qualitative and quantitative indicators of biogas. As a result, it has been found that biomass type affected the methane percentage in biogas greatly. The methane content of biogas independent with biomass type was diminished from 65% (galega) to 44.5% (fresh sawdust), but biogas yield decreased from 0.627 m**3 kgVSd E-1 (galega) to 0.185 m**3 kgVSd E-1 (fresh sawdust).

A lot of different EU directives and regulations set the targets to decrease greenhouse gas emissions, to increase the share of renewable energy, and to improve energy efficiency. Biofuel usage is directly linked to all of these problems. Since the first generation food-based biofuels should not receive public support after 2020, investigations of next generation biofuels are topical. Hydrotreated vegetable oil (HVO) is one of the most promising next generation biofuels in the near future. This article deals with the results of mathematical modelling to determine the main diesel engine operating parameters (power, torque and fuel consumption) running them on HVO and its blends with fossil diesel fuel. The modelling results of the car Opel Insignia 2.0 CDTi show that every 5% of HVO in fuel blend reduces maximum power and torque of around 0.38% while raising specific fuel consumption by volume of around 0.10%. Analyzing the most realistic scenario in the near future – 7% HVO and 93% fossil diesel blend, the predicted fuel consumption increase (0.14%) and power and torque decrease (0.54%) is inconsiderable for vehicle exploitation, and HVO seems to be a promising biofuel to replace biodiesel in fuel blends and to promote reaching the EU targets.

To promote the future of abandoned lands management and the reduction of fossil energy consumption in Latvia, the establishment of energy crops plantation facilities, including perennial grasses, was investigated. The objective – suitability of several perennial grasses for bio-energy production under condition of Latvia. The aim of the current research to evaluate the experimental field conditions for the cultivation of perennial grasses. The perennial grasses are modest in terms of soil conditions, they are environmentally friendly, as well as provide high yields of biomass with adequate quality for bio-energy production without large investments. With increasing amounts of bio-energy production the amounts of various by-products which are profitable to utilize as energy crops fertiliser will also increase. It is essential that plant nutrients return back into circulation by creating a complete cycle. In order to test in practice the possibility of creating this complete cycle of growing perennial grasses, an experimental field was chosen at the Research Institute of Agriculture in Skriveri. In the summer of 2011, before trials establishment, the conditions of soil were examined at four depths: 0 – 20 cm; 20 – 40 cm; 40 – 60 cm and 60 – 80 cm. The analyses showed that the experimental field conditions were appropriate for growing of perennial grasses. The results of the soil agrochemical analysis will be a base for future studies of usage efficiency of different fertiliser types on perennial grass productivity and nutrient recycling opportunities in energy crop plantations.

The study represents results of productivity studies of mechanized ditch cleaning using Ponsse Fox harvester adapted to multi-tree handling H6 head in forest drainage systems managed by Joint stock company “Latvia state forests”. The aim of the study is to evaluate productivity of extraction of biomass from ditches depending on working method and to estimate factors affecting prime-cost of biofuel in mechanized harvesting. The study results demonstrate that the 2nd method (mechanized extraction of roundwood and following motor-manual cleaning of remaining vegetation) is the most efficient solution for mechanized cleaning of ditches. Benefits of the 2nd method are smaller costs of undergrowth removal and bigger output of solid biofuel. Ponsse Fox harvester demonstrated sufficient work quality and productivity in the trials; however, it would be wise to use heavier harvesters or caterpillar excavator based harvesters in ditch cleaning. Using the 2nd method, a harvester can extract about 227 ha of ditches (23,000 m3 ) annually.