IS IT A VIABLE ALTERNATIVE?

FIROZ ALAM, ABHIJIT DATE, ROESFIANSJAH RASJIDIN, SALEH MOBIN, HAZIM MORIA, and ABDUL BAQUI

4.1 INTRODUCTION

The global climate change, rising crude oil price, rapid depletion of fossil fuel reserves, and concern about energy security, land and water degrada­tion have forced governments, policymakers, scientists and researchers to find alternative energy sources including wind, solar and biofuels. The bio­fuel production from renewable sources can reduce fossil fuel dependency and assist to maintain the healthy environment and economic sustainabil­ity. The biomass of currently produced biofuel is human food stock which is believed to cause the shortage of food and worldwide dissatisfaction especially in the developing nations. Therefore, microalgae can provide an alternative biofuel feedstock thanks to their rapid growth rate, greenhouse gas fixation ability (net zero emission balance) and high production capac­ity of lipids as microalgae do not compete with human and animal food crops. Moreover, they can be grown on non-arable land and saline water. Biofuels are generally referred to solid, liquid or gaseous fuels derived from organic matter [1]. The classification of biofuels is shown in Fig. 1. These classifications are: a) Natural biofuels, b) Primary biofuels, and c) Secondary biofuels. Natural biofuels are generally derived from organic sources and include vegetable, animal waste and landfill gas. On the other hand, primary biofuels are fuel-woods used mainly for cooking, heating, brick kiln or electricity production. The secondary biofuels are bioethanol and biodiesel produced by processing biomass and are used in transport

о CO

Produced from — Firewood, plants — Wood chips — Forest — Animal waste — Landfill gas — Crop residues

Biodiesel produced from — Microalgae — Mircobes

Bioethanol produced from — Wheat, barley, corn — Potato, sugarcane, beet — Oil seeds (soybeans coconut, sunflower rape seed — Animal fat, used cooking oil /

Bioethanol & Biodiesel produced from — Cassava, jatropha miscanthus — Straw, grass, wood

FIGURE 1: Biofuel production sources (biomasses) (adapted from [2])

sectors [1]. The secondary biofuels are sub classified into three so called generations, namely, a) First generation biofuels, b) Second generation biofuels, and c) Third generation biofuels based on their different features such types of processing technology, feedstock and or their development levels [2].

Despite having potential in producing carbon neutral biofuels, the first generation biofuels possess notable economic, environmental and political concerns. The most alarming issue associated with first generation biofu­els is that with the increase of production capacity, more arable agricultur­al lands are needed for the production of first generation biofuel feedstock resulting in reduced lands for human and animal food production.

The increased pressure on arable land currently used for food produc­tion leads to severe food shortages, especially in developing countries of Africa, Asia and South America where over 800 million people have been suffering from hunger and malnutrition from severe shortages of food. With the growing world’s population, the demand for food is increasing — while the arable land is decreasing. The intensive use of fertilizer, pesti­cides and fresh water on limited farming lands can reduce not only the food production capacity of lands but also cause significant environmental damage [15]. Therefore, enthusiasms about first generation biofuels have been demised. Increasing use of first generation biofuels will inevitably lead to increasing the price of food beyond the reach of the under privi­leged. The political consequences of this could be difficult to contain.

As first generation biofuels are not viable and receive lukewarm re­ception, researchers focused on second generation biofuels. The primary intention here is to produce biofuels using lignocellulosic biomass, the woody part of plants which do not compete with human food chain di­rectly [2]. As shown in Fig.1, main sources for second generation biofuels are predominantly agricultural residues, waste (e. g., trimmed branches, leaves, straws, wood chips, etc.) forest harvesting residues, wood process­ing residues (e. g. saw dust) and non-edible components of corn, sugar­cane, beet, etc. However, converting the woody biomass into fermentable sugars requires sophisticated and expensive technologies for the pretreat­ment with special enzymes making second generation biofuels economi­cally not profitable for commercial production [2, 4].

Hence, the focus of research is drawn to third generation biofuels. The main component of third generation biofuels is microalgae as shown in

Fig. 1. It is currently considered to be a feasible alternative renewable en­ergy resource for biofuel production overcoming the disadvantages of first and second generation biofuels [1- 2, 5, 16]. The potential for biodiesel production from microalgae is 15 to 300 times more than traditional crops on an area basis [2]. Furthermore compared with conventional crop plants which are usually harvested once or twice a year, microalgae possess a very short harvesting cycle (1 to 10 days depending on the process), allow­ing multiple or continuous harvesting with significantly increased yields [2, 15]. Additionally, the microalgae generally have higher productivity than land based plants as some species have doubling times of a few hours and accumulate very large amounts of triacylglycerides (TAGs). Most im­portantly, the high quality agricultural land is not required for microalgae biomass production [3].