Contents Biodiesel Production From Algae

Published Date: 02 Nov 2017

Chapter 1

1- Introduction

Motivation

As petroleum prices increases and the pressure of environmental concern in reducing greenhouse gas emission that causes global warming, the race is on to develop a renewable energy source that is economically viable.

Currently the world very much depends on fossil fuel as the main transportation fuel, for example United stated alone has last year used about 64 billion gallon of diesel fuel for transportation (IEA 2007), at this amazing level use of petroleum fuel, according united state Energy information administration to the world’s petroleum reserves will be exhausted in the next 30 to 40 years the and even more incredible is as a result of the huge consumption, the transportation sector is accountable for the huge amount of green house gases emission which is the source of global warming as well as the atmospheric pollution around the world. Therefore a practical energy supply that eliminate petroleum, power the transportation system and ease green house gases must be established. Fig 1.1 below shows the expected drastic fall in the supply of fossil fuel by the year 2030.

Fig forecast of petroleum depletion

For several years attempt were made to come up with alternative method of renewable energy from wind, solar and nuclear among others but failed to provide alternative that was capable enough to provide a renewable energy source. First and second generation bio-energy crops are not able to address the increasing demand, as land resource are limited , environmental problems arising from deforestation is a grave concern. Using arable land for bio-fuel production creates food vs fuel completion and finally the benefit of mitigating climate change is negligible (Mehta and Gair2001). Therefore developing a renewable energy industry that is viable, sustainable, competitive and cost effective remains a challenge.

Biodiesel is a tested technology and a tremendously attractive option fuel source which can be made from any vegetable or fat oil. At present the bulk of this diesel for example in U.S came from soybeans. This system currently offer an energy benefit, provide a considerable reduction in GHG and can be used in the current diesel cars with slight modification, however the major setback of these system is that there is less biodiesel produced in an acre of land which means if all of the soybeans grown in the U.S were to be used for the production of biodiesel it will not meet the present level of diesel consumption.

So as to justify biodiesel to be the supply of energy to our transportation requirements a novel superior yielding source of biodiesel have to be discovered. Microalgae are extraordinarily competent plant able of taking a waste form of CO2 and converting it into natural oil. Microalgae were found to have unbelievable production rank compared to oil seed crop like soybean. This why this project is interested in the production of biodiesel from algae and propose a cost effective method for its economic viability.

One of the most promising processes is the conversion of algae into fuels, since algae do not totally compete with agricultural water demand; the likely hood for algae to sustainably supply bio-energy in contrast with other bio-fuel crops looks promising.

The notion of using algae as an alternative energy source of fuel has been there for well over thirty years but due to setback in algae cultivation and the lipid extraction process, the development of algae-to-fuel process was considerably slow as compared to other source of renewable energy.

Algae yield nearly thirty times more energy per acre than any other feedstock crops, mainly because algae are grown in suspension, giving it better access to water, CO2 and other nutrients (Sheehan et al. 1998). Of the various alternative fuel technologies, the conversion of algae has the most promise as a fuel source as it provides a wide variety of fuels. Despite algae having several unmatched advantages as alternative source of energy over other renewable energy, the viability of algae in terms of sustainability and economic is subject to a thorough research and debate. The hurdle is that the process of producing bio-fuel from algae is an energy intense process meaning that there is more energy input in the algae fuel production process than the output hence hindering its economic viability. solving the issue relating to the economic viability of algae bio-fuel production is beyond the reach of this project however the researcher believe that most of the cost involve in the production can be reduce by maximising the physical process involve in the production of algae bio-fuel and hence meeting the project aim of making the biodiesel production process a cost effective and hence economic viability.

Since experimentation was not easy due to the current climate of the year in which the project was under taken, the aim of the project is therefore to investigate algae biodiesel production processes and explore options for process optimisation which will be carried out based on existing literature. Also since little is known about the environmental consequence of algae bio-fuel production this project also aim to undertake detail environmental analysis on large scale production and its sustainability in terms of land, C02 emission, water requirement and compared to various established bio-fuel crops so as to get a clear indication of it advantages and limitation

Therefore this project explore the process of producing biodiesel from algae such as cultivating algae, harvesting and extraction of oil from algae, and in order to make the process a cost effective, the project proposes a novel idea of integrating algae biodiesel production facility with wastewater water treatment plant and sugarcane mill plant, to provide the process with the required nutrient and energy plus CO2 respectively.

Chapter one discusses the important of algae strain selection that has high lipid content algae and site selection which make algae cultivation for biodiesel easy and controllable . Chapter 2 discusses the various technology that makes up the algae biodiesel production are discussed; algae cultivation technology; processing to biodiesel options; and the physical input such as carbon dioxide, light, temperature water and nutrient among others.

Chapter 3 discusses the economic viability- how to make algae biodiesel production cost effective and economic viable, by looking at incorporating the algae biodiesel production facilities with wastewater treatment plant to provide the necessary nutrient at less cost and also incorporating the sugarcane mill to provide water, CO2 and energy.

Chapter 4 Sustainability of algae base biodiesel is look into depth, the chapter will first start with evaluating the sustainability of the already existing biodiesel feedstock and then followed by a thorough evaluation of risk and opportunity of algae sustainability and lastly the sustainability in context to the potential and threats to the developing countries analysis (Smeets et al. 2009)

Algae as a renewable energy

Why algae

There are many advantages of using algae for biodiesel production in comparison with other available feedstock..

Algae does not compete for arable land as well the use of nutrients required for conventional crops

Algae have high yield biomass per acre of land compared to agricultural crop land (see the table below shows some comparison of different feedstock

algae have the ability to grow on land unsuitable for agriculture

algae has the ability to utilise salt water and waste water

algae can be harvested throughout the year

can recycle carbon from CO2 emission

algae can be used in combination with water treatment (WWT)

Algae also offer feedstock for a number of diverse types of renewable fuels such as biodiesel, hydrogen ethanol and methane, among others.

Algae biodiesel perform well like petroleum diesel and have no poisonous gas such sulphur dioxide ( Chisti 2007). The below Table 1.1 shows the oil content and yield as well as land requirements for different range feedstock and algae top the list with about having 70% oil contents. ( Chisti 2007).

Table1.1 Comparison of oil yield from different feedstock adopted from ( Chisti 2007)

However despite all of the above advantages the cultivation of algae for bio-fuel or for any other use, are not without disadvantages. The process of producing bio-fuel from algae is belief to be energy intense, meaning that the process need more energy input that the energy output. That being the case fresh water and energy demand for algae cultivation production must be reduced, it’s therefore essential to use nutrient and CO2 from other source at no cost or at cheaper price. This project propose to tackle these challenges in the following way

so as to reduce the demand for fresh water the algae can be grown on waste water this process also assist recovering the required nutrient for algae at no cost.

CO2 can either be recycle or obtained from the flue gases nearby industrial site such as sugarcane mill plant

From economic point of view, it’s not economically feasible to produce bio-fuel particularly biodiesel from algae with the current technology and so this project the novelty of integrating the algae bio-fuel production with wastewater treatment plant and sugarcane mill. The objective of the project is therefore to carry

Produce an algal biodiesel production process incorporating state of the art processing technologies.

Identify bottlenecks of the algal biodiesel production process.

Evaluate the resources required for algal biodiesel production and resources available at wastewater and sugarcane mill processing plant

What is Algae

Algae are the term normally referred to a different mix of organisms. Usually algae are group based on their ability to carry out photosynthesis and how they normally live in aquatic habitats. Algae can be single or multi-cellular and pro- or eukaryotic (Richmond 2004)

Algae are normally divided into two groups , the microalgae (unicellular eukaryotic organisms), macro algae (seaweeds), and cyanobacteria (historically known as blue-green algae), because of their diverse characteristics, the type and strain of algae being cultivated will ultimately affect every step of the algae to bio-fuels supply chain (Richmond 2004). In this project the use of the word algae refers to the microalgae group.

Species Selection

Spices selection is a important factor and is the first step in the algae bio-fuel production process. There are almost thousands of well known algae species with broad range properties it is therefore vital to have a broad idea of what of these characteristic are most suitable before choosing the algae species. (Sheehan et al.1998a).

Since the focus of this project is on the production of biodiesel from algae a possible significant factors to consider is algae species that have a high oil content well as high growth rate The oil content of algae can vary from as low as 5% to 70%, while the growth rates can vary from as low as 3.5 hours to several days (Metzger 2005).

Other factors that are also crucial in the species selection is the ability of algae to thrive under intense condition such as high temperatures, salinity and the pH. By profiling the above set criteria on the selection of algae species the quality of the fuel can be predicted even before the large scale cultivation (growth) of algae (Miao 2006), this therefore indicate the significant role spices section plays in the optimisation of bio-diesel production process hence its economic viability.

Algae selection of site and the climate

Site selection is a vital step that ultimately influences the economic viability of algae biodiesel production process. According to Maxwell et al. to operate an algae cultivation, a site selection and resource evaluation have to be carried out such as water supply and demand, nutrient and CO2 supply, condition of the climate in terms temperature radiance and evaporation rate.

Seasonal variation affects the productivity of algae and so the selection of good climate in algae cultivation is vital this been the case investigating the solar radiation as well as the air temperature is paramount.

The temperature in the air affect the temperature of the water, depending on the geographical location, a suitable temperature ranges between 20-35 °C is preferred (Park et al. 2011) Figure1.1 below shows the world temperature zone, the region within the rectangle box shows a desirable temperature zones for high algae productivity, while the region that fall within the blue zone has low temperature minus 15 °C below the required 15 °C temperature hence unfavourable for algae cultivation (Lundquist et al. 2010). However this can be solved by providing the algae culture excess heat to warm up the pond cultivation.

Also in places where the temperature is high over 40 °C is not an optimal temperature for algae cultivation as it may result in evaporation and water lost particularly in open algae cultivation (Lundquist et al. 2010). Needs a bit of revision

Chapter 2

2.1- Algae Bio-fuel production

In order to explore algae biomass production and its related solar effectiveness it is important to have an idea of the underlying photosynthesis that is taking place which convert the solar energy in to chemical energy.

In general photosynthesis reaction is summarised as an endothermic reaction between CO2 and water to form glucose and oxygen, in which light is used for the required energy. Solar Energy is thus stored in energy rich glucose, a compound that serves as the basic .............

A sustainable cultivation of algae for bio-fuel production depends on several factors such as land, water and nutrients, these factors also determine its effect on the environment. Cultivation of algae for bio-fuel production dates back in the fifties , however more research was launched in 1978 by the aquatic species program from the United States Renewable Energies Laboratory (NREL) which thoroughly explored a large scale cultivation of algae for bio-fuel production concluded that it was it was possible to but not economically viable. (Sheehan et al.1998a).

Bio-fuel production from algae can be categories in two, the cultivation stages and the biomass conversion stage, in first stage algae is cultivated (grown ) and

biomass is produced. The other stage is the conversion stage where the biomass produced is converted into an energy product. Figure 1.2 below shows schematic view of algae biodiesel production and a stage by stage review of the different aspects that are involved in the process of algae cultivation and subsequent conversion of biomass is out line thereafter.

Fig 1.2 Schematic view of the detailed biodiesel production processes (http://www.oilgae.com/ref/report/report.html)

2.2 Algae Cultivation

Algae can be cultivated into two forms under autotrophic(light dependant) uses light energy to make photosynthesis or under the heterotrophic (non dependant) but for the purpose of this project, this report focuses on processes optimisation to make the process cost effective will concentrate on heterotrophic which freely uses the sunlight (Brennan and Owende 2010).

Successful light dependant algae cultivation depends on various factors that make up culture environment. These factors include availability of light, nutrient, pH and temperature and to achieve optimum yield, optimising these conditions in a way that there are no major limiting issue will be advantageous( Chisti 2007) However a lot of these factors can be easily optimise by selecting a suitable location

Generally there are two ways in which algae can be cultivated. The open system and closed systems. In an open system, the medium which is the term referred to the aquatic environments is kept in the open atmosphere and not isolated from the environment while in a closed system, the medium is isolated from the external environment in what is known as a photo-bioreactor (PBR) 

2.2.1-- Open pond systems

The raceway is the most common design of open pond cultivation system

This is basically a shallow, raceway shaped pond in which the culture medium is mechanically circulated using a paddle wheel or pump. This agitation is necessary to prevent settling, increase overall light availability and to increase gas exchange. The depth of these ponds is usually limited to 10-30 cm which allows for sufficient light penetration at high cell densities. Although simple in their design, the fact that these systems are in direct contact with the environment, makes it hard to control culture conditions and easy for other species such as non-suitable algae and other invasive species to enter the system hence reduce productivity (Sheehan et al. 1998a)

So although high yields of up to 70 g/m2 /d were sometimes achieved, such results are often based on a few days in summer only and hard to maintain. A more realistic approach arises when overall yearly averages are recorded. And maximum annual yields that have been reported for such open systems are around 20-25 g/m2/d. Authors of the Aquatic Species Program concluded that overall long term average yields of around 20 g/m2/d were more realistic (Sheehanet al. 1998a).

2.2.2- Closed cultivation systems

In a closed cultivation system the medium is isolated from of the environment and hence fairly easy to keep a monoculture of a single species and to control environmental conditions. There are normally three common photo-bioreactor designs (Eriksen 2008;Pulz 2001; Ugwu et al. 2008). The tubular photo-bioreactors, vertical column photo-bioreactors and flat-plate photo-bioreactors

 Vertical column bioreactors consist of a transparent vertical column of up to several meters high. Mixing and aeration is commonly achieved by injecting an air or an air/CO2 mixture that is bubbled from the bottom of the column. This bubbling effectively is a cheap and easy method to prevent the accumulation of oxygen, provide additional CO2 for photosynthesis, and to ensure that the cells are kept in suspension. However such systems are very costly and are therefore not suitable for large scale production.

Tubular photo-bioreactors however are more common for larger scales. These systems consist of long plastic tubes with a diameter anywhere between 5 and 30 cm. These tubes can either be placed in horizontal arrays on the ground or vertically in fence-like constructions. Mixing and mass transfer are achieved by pumping the culture through the tubes. The disadvantage however is that the length of the long tubes can cause accumulation of CO2 and nutrient.

However this can be prevented by pumping the culture regularly But this will bring considerable cost for large scale systems. Another known problem is that pumping the water through extended lengths of tubes can cause considerable cell damage. Smaller diameters give better productivity, but increase the pumping energy inputs exponentially.

Flat-plate or photo-bioreactors consist of flat and hollow plastic panels through which water flow is controlled by internal channels. Thickness is normally between and 1 and 10 cm, which allows for high cell density while still achieving good light penetration. Like solar panels they can be placed at optimal angles for maximum irradiance, which would increase incoming radiation, but also brings additional costs. So far typical outdoor yields between 30-48 g/m/d have been confirmed with these typical bioreactor designs. Various new designs that are based on above principles are being commercially explored at the moment. (Figure 2) (Pulz, 2007).

The suspension of the bags does require quite some costly structural components, making it not directly suitable for large scale application, but nevertheless the result seems to be quite promising.

All in all, both open pond and photobioreactor systems have their own advantages and disadvantages (Table 5). In general it can be said that open system are much cheaper to construct ,but do not allow much control of the culture conditions, whereas a closed system is expensive but gives much better control and as such it can give higher average yields. Since there are various arguments for either of these systems, ultimately design will depend on a combination of many of these factors, but also the location, the type of algae and the desired scale of the system.