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.

The European Parliament and Council Directive 2003/30/EK ‘On the promotion of the use of biofuels and other renewable fuels for transport’ determines that pure or straight vegetable oil, produced from oil plants by pressing, extracting or comparable procedures, crude or refined but chemically unmodified, compatible with common engines, and corresponding to emission requirements, is also considered as biofuel. The biggest problems imposed by these conditions are directly associated with the carrying-out of the emission requirements, because when using vegetable oil as a fuel, usually increases the composition of the solid particles and nitrogen oxides in exhaust gases, that not only adversely affect the environment, but also is a serious threat to human health, and as a result trying to save the world from the global warming, human health continues to deteriorate. It is therefore necessary to carry out studies and find solutions to reduce harmful emissions from diesel engines when using vegetable oil fuel. For more qualitative and effective research on vegetable oil fuel emissions, the equipment for vegetable oil fuel testing has been developed. This equipment allows fast checking of theoretically proposed hypotheses and detailed calculations for vegetable oil fuel combustion processes and objective data acquisition. The equipment consists of the classic diesel engine adapted for work with vegetable oil and is equipped with several high-precision devices to get and store the measuring data. During pilot tests the optimal measuring modes (engine rotation frequencies, number and duration of repetitions) for further research are estimated.

Biodiesel is renewable and environmentally friendly fuel, which can be used as a substitute for diesel in compression ignition (CI) engines. Nowadays it is also successfully used not only in transport sector, but also in commercial construction equipment and space heating. As the production of biodiesel (rapeseed methyl ester RME) is started now and is planned to grow rapidly, it is necessary to investigate biodiesel impact on engine performance and exhaust gas composition. This paper describes results of the investigation the aim of which was to find out the impact of biodiesel and its blends on an engine's dynamical, economical and ecological parameters in laboratory conditions on an engine test bench. The experimental work was done with an XD2P diesel engine in the Motor testing and biofuels laboratory of the Motor Vehicle Institute of Latvia University of Agriculture. The engine was fuelled on fossil diesel, rapeseed methyl ester (RME) and on blends of 5 (5RME) and 35 (35RME) percent RME/diesel fuel. The results indicated that power for biodiesel and blends was lower than with ordinary petrol diesel on average. 7.9% on 100RME and 3.6% on 35RME. The reduction in torque and increase in fuel consumption was observed. Experimental results showed that the addition of RME to diesel can significantly reduce oxides of nitrogen (NOx), carbon monoxide (CO), and absorption coefficient.

Lowering emissions expelled from internal combustion engines has been the focus of researchers worldwide. Adding hydroxy gas to current internal combustion engines can be an effective way of lowering CO2, CO, HC and particle emissions, as well as improve combustion. Because of this, a review of previously conducted research on the addition of hydroxy gas to different internal combustion engines has been produced. During this review, it was concluded that addition of hydroxy gas can be an effective way of lowering fuel consumption and CO, CO2 and HC emissions in petrol engines, as well as fuel consumption and CO and HC emissions in diesel engines.