Microalgae biofuels for diesel engines in agricultural applications

Microalgae biofuels for diesel engines in agricultural applications

Diesel engines are the key components of several sectors in modern life. The dramatic growth of the world’s population, economy and industry has increased the demand for petroleum diesel (PD) fuel. The increased use of depleting PD in recent years has highlighted the problems of high fuel prices and emissions. The emissions from combusting PD have been proven to affect human health and to contribute to the high carbon dioxide (CO2) emissions that have led to global warming.

Alternative fuels have become essential for eliminating the PD problems. Biodiesel has attracted much attention as a renewable and environmentally friendly alternative fuel. The main drawback of using biodiesel as a fuel alternative to PD is the limited resources available, which cannot satisfy the demand for PD. Using vegetable oil for biodiesel purposes could create a food crisis. Potentially, microalgae are a promising alternative because of their high biomass and lipid productivity, and because they can contribute to reducing CO2 pollution through the photosynthesis process. Microalgae have the ability to grow in a variety of difficult conditions such as in seawater, wastewater or deserts, thus avoiding influence on the agriculture sector.

In this work, fresh water microalgae Chlorella vulgaris (FWM-CV) was grown for biodiesel production and to study the effect of enhancing the lipid content using iron as stress treatment on the biodiesel properties. Different growing conditions were found to give different fatty acid methyl ester (FAME) components, which led to different biodiesel properties. However, this biodiesel was found to have acceptable properties for running diesel engines.

Single-cylinder diesel engine performance and exhaust gas emissions were evaluated using microalgae Chlorella protothecoides MCP-B100, MCP-B50, MCP-B20 and PD. The overall results indicated that MCP-B100 and its blends have fuel properties, engine performance and enhanced emissions comparable to those of PD. Statistical analyses showed that the effect of the fuel type on the studied parameters was statistically significant except for the fuel consumption (FC) rate, thermal efficiency and CO2. MCP-B100 produced a reduction by 7%, 4.9%, 28% and 7.4% in the brake power, torque, CO and NOx, respectively, and an increase by 10.2% and 15.8% in the brake specific fuel consumption (BSFC) and oxygen (O2), respectively.

A second test was performed to study the effect of adding FWM-CV cells to enhance the energy content of emulsified water fuels on the performance and exhaust gas emissions of a single-cylinder diesel engine. The test was conducted using cottonseed biodiesel (CS-B100), emulsified water fuel in cottonseed biodiesel (CS-E20) and emulsified water fuel containing FWM-CV cells (CS-MB100). The general findings were that the CS-MB100 presented higher results of gross input power, brake power, torque, CO2 and nitrogen oxide (NOx) than CS-B100 and lower results than CS-B100. These findings indicate that the addition of FWM-CV cells to emulsified water fuel has a positive effect on fuel properties and engine performance.

An agricultural tractor power take-off (PTO) test was conducted using MCP-B20 to examine the performance and exhaust gas emissions under different operating conditions. The results indicated an insignificant difference in engine performance when MCP-B20 was used compared with PD. However, the analysis of variance (ANOVA) summary at rated PTO speed showed a significant reduction in the values of torque, power, carbon monoxide (CO), CO2 and nitrogen monoxide (NO), and a significant increase in the O2 lambda for MCP-B20 compared with those of PD.