Algal biofuel production and mitigation potential in India

ORIGINAL ARTICLE

Algal biofuel production and mitigation potential in India

H. N. Chanakya & Durga Madhab Mahapatra &

R. Sarada & R. Abitha

Received: 13 February 2012 /Accepted: 19 April 2012 /Published online: 24 May 2012# Springer Science+Business Media B.V. 2012

Abstract Energy and energy services are the backbone of growth and development in India andis increasingly dependent upon the use of fossil based fuels that lead to greenhouse gases (GHG)emissions and related concerns. Algal biofuels are being evolved as carbon (C)-neutralalternative biofuels. Algae are photosynthetic microorganisms that convert sunlight, water andcarbon dioxide (CO2) to various sugars and lipids Tri-Acyl-Glycols (TAG) and show promise asan alternative, renewable and green fuel source for India. Compared to land based oilseed cropsalgae have potentially higher yields (5–12 g/m2/d) and can use locations and water resources notsuited for agriculture. Within India, there is little additional land area for algal cultivation andtherefore needs to be carried out in places that are already used for agriculture, e.g. flooded paddylands (20 Mha) with village level technologies and on saline wastelands (3 Mha). Cultivatingalgae under such conditions requires novel multi-tier, multi-cyclic approaches of sharing landarea without causing threats to food and water security as well as demand for additional fertilizerresources by adopting multi-tier cropping (algae-paddy) in decentralized open pond systems. Alarge part of the algal biofuel production is possible in flooded paddy crop land before the cropreaches dense canopies, in wastewaters (40 billion litres per day), in salt affected lands and innutrient/diversity impoverished shallow coastline fishery. Mitigation will be achieved throughavoidance of GHG, C-capture options and substitution of fossil fuels. Estimates made in thispaper suggest that nearly half of the current transportation petro-fuels could be produced at suchlocations without disruption of food security, water security or overall sustainability. This shiftcan also provide significant mitigation avenues. The major adaptation needs are related tosocio-technical acceptance for reuse of various wastelands, wastewaters and waste-derivedenergy and by-products through policy and attitude change efforts.

Keywords Algal biofuel . Wastewater algae . Paddy-algiculture . Multi-tier . Multi-cyclicalgiculture . Algal biomethane

Mitig Adapt Strateg Glob Change (2013) 18:113–136DOI 10.1007/s11027-012-9389-z

H. N. Chanakya (*) : D. M. Mahapatra : R. AbithaCentre for Sustainable Technologies, Indian Institute of Science, Bangalore 560012, Indiae-mail: [email protected]

R. SaradaPlant Cell Biotechnlogy, CFTRI, Mysore 570020, India

1 Introduction

The global energy demand, especially petroleum derived fuels (PDF), has been increasing atan unprecedented rate with an increasing pressure on the utilities of fossil based fuels. Thisincreased usage of fossil fuels, especially dependence of the development process on PDF isconsidered unsustainable for several reasons. The most important reason is the increasedlevels of greenhouse gases (GHG) emissions (Hill et al. 2006). Increased rates ofPDF-dependent development have been argued to hasten the process of climate change.Thus a shift to renewables will not only slow down this trend but will ultimately lower thenet carbon dioxide (CO2) levels and reverse climate change trends. Along with carbondioxide (CO2) are concerns of increased generation of wastewater and its discharge ininadequately treated conditions. Such wastewaters have plenty of plant nutrients such asnitrogen (N), phosphorus (P) and potassium (K) (together called NPK). As most fertilizers(especially N based ones) are manufactured at the expense of fossil fuels – petroleum derived ornatural gas, a lot of current research envisages to raise algae on these wastewaters to firstlygenerate algal biomass for petroleum like fuels, second recover and recycle high energycontaining N (and scarce P) from wastewaters and third treat wastewaters without simultaneousemissions of methane a potent GHG. There is thus an increasing need for strategies andtechnologies that help in generation of renewable energy from algal cultivation that makebiofuels C-neutral (Hill et al. 2006; Rittmann 2008; Demirbas 2009) and at the same time treatwastewater (Woertz et al. 2009; Pittman et al. 2011; Devi et al. 2012).

For some time now, crop-based biofuel alternatives have been considered to be economicand competitive compared to fossil fuels. However, when compared to the potential fromalgal biofuels, the energy returns from land based oil-seed crops are less because of lowproductivities (Khan et al. 2009), etc. Further, it is generally seen that terrestrial biofuelcrops compete with conventional food crops for land area and other resources and thereforepose a threat to food security of the region (Hill et al. 2006; Demirbas. 2009). Algal biofuelson the other hand appear to be a potential alternative that seemingly does not impact theagriculture and has the added advantage of an ability to grow in extreme environments thatare not considered suitable for conventional agriculture and yet possess high productivities(Singh et al. 2011). The increased volumes of wastewater as well as a discharge of partiallytreated wastewater by rapidly urbanizing areas of developing countries have posed a seriousthreat of pollution of surface and ground water resources. New technologies to use variousforms of nutrient laden wastewaters to generate algal biofuels with simultaneous waterpurification will reduce water pollution problems of rapidly urbanizing cities and help waterintensive agriculture.

Algae derived biofuels promise substitute for PDF under laboratory and pilot plantconditions - a classic estimate to substitute US PDF needs suggests that only 0.49 % ofland area of United States (US) is required (Hartman 2008) assuming that algae will begrown in near desert like lands (wasteland) using brackish water unfit for agriculture(Sheehan et al. 1998) and with little threat to food security or environment and the processis thus considered in this context quite sustainable. Similarly, various studies in India projectbiofuel potential of India using marginal and wastelands (Jatropha and various tree crops) tobe sustainable to generate biofuels to meet India’s energy needs (Kumar and Sharma 2005).While studies with respect to woody biomass cultivated on wastelands have assumed aproductivity of 4 t/ha/yr as woody biomass (Reddy 1994), 4–10 t/ha/yr for oilseed crops(Abhilash et al. 2010), the estimates for algal biomass derived fuels appear alluring at 36 t/ha/yr (Dayananda et al. 2006; Centre for Sustainable Technologies unpublished report)going up to 125–175 t/ha/yr (Chisti 2007) and is therefore much more attractive to pursue

114 Mitig Adapt Strateg Glob Change (2013) 18:113–136

and review. Most of such studies on biofuels have attempted to address sustainability issuesemerging from threat to food security (Singh et al. 2011) or as a means for regeneration ofwastelands (Khan et al. 2009).

When a large scale shift to biofuels needs to be considered in India, using for examplemarginal and wastelands, the sustainability threats emerge in multiple domains and arecomplex. They need to be studied individually and addressed collectively so that potentialalternatives or options could be found. The issues of sustainability then transcend merearguments on the availability of land for cultivating such biofuels. For example, issues ofproviding mineral nutrition, the large volumes of water needed, pests and diseases, controland managing of process wastes and many other social and economic dimensions ofsustainability assume importance. Considering that every kg of algal biofuel would needbetween 0.3 and 0.5 kg N to be supplied to algal ponds, identifying the additional fuelsources to synthesize additional N fertilizer for growing algae becomes vital. Further,because about 2 kg fossil fuel is used up to synthesize 1 kg of N, in the above context ofthe N and other nutrient requirement for algal biofuel production, the overall energeticscould become negative unless sustainable alternatives to this issue are evolved. Energy-intensive laboratory and pilot plant studies have often raised the expectation of the potentialof algal biofuels, especially for developing countries such as India. It is therefore vital that,for large-scale algal cultivation, we obtain a realistic estimate of potential algal biofuels thatcan be raised sustainably in India considering the above limitations. The objectives of thepresent study are thus to estimate the potential to sustainably raise algae and algal biofuels inIndia and determine the mitigation potential of such a possibility. An attempt is also made todetermine the required technologies, potential adaptation needs, list sustainability determinants,etc. of the above options.

2 Hydrocarbon fuel needs for India

In India, like many developing countries, the development process depends upon PDF. Urbantransport system has become increasingly dependent upon PDF (Reddy and Balachandra2012), agricultural practices have become increasingly mechanized and PDF dependent(Baruah and Bora 2008; Figs. 1 and 2) which is expected to rise and remain high (Singh2006). On the one side, oil and gas as fuels (45 % of total energy) is considered vital todevelopment (transport sector -MoPNG 2007, Figs. 1 and 2 where crude oil consumption hasreached 180 million tons of oil equivalent, Mtoe). On the other, about 30–40 % of the primaryenergy comes from biomass and therefore its utilization and cultivation can be coupled tosimultaneous algal biofuel production (Chanakya et al. 2009; 2012 >80 % of PDF is imported).The increasing trends of crude oil prices have increased efforts to identify cost-effective andrenewable energy alternatives, especially going towards a global trend for biofuels (Khan et al.2009) Figs. 3 and 4.

One approach to continued use of PDF is to sequester large quantities of carbon (C) to offsetthe increasing level of CO2 emissions while functioning at current level of PDF use. Thisstrategy requires adoption of C-sequestering technologies, minimizing fossil-fuel dependencythereby fostering environmental and economic sustainability (Prasad and Elnashaie 2004;Brennan and Owende 2010; Singh et al. 2011). It is anticipated that India and other developingcountries will soon attempt to reduce their C footprints and emission of GHGs through PDFreduction and C-sequestration. Biofuels are then considered C-neutral/C-negative and can playa critical role in meeting targets to replace PDF transportation fuels (Yuan et al. 2008). Liquidfuels used in transport sector can then directly be replaced by these clean C-neutral biofuels

Mitig Adapt Strateg Glob Change (2013) 18:113–136 115

such as algal biodiesel or methane (Carere et al. 2008; Escobar et al. 2009; Singh et al. 2011; Pantet al. 2010). In recent years, there has been increased usage of liquid biofuel in the transportsector because of various policies to safeguard energy security and mitigate GHG emissions(IEA 2007).

Estimates of the mitigation potential have been made from primary data on land area andland use, water resources and rainfall patterns, etc. available at various government and non-government databases. The productivity data of various algal species of India has beencompiled from various published sources starting from the period of extensive use of blue-green algae to current marine algae on shallow coastal waters. However, even though there isplenty of information of algal occurrence and distribution, there is very little data on growthand productivities under laboratory and field conditions of India. We therefore rely largelyon our own field and laboratory estimates arising from studies on algal growth in river, lakeand wastewaters as well as from personal communications from contemporaries. Apart fromthis there is little experience in India on growing green algae for biofuels – green algae inpaddy fields or in wastewater treatment plants have generally been treated as weedspartaking of the natural fertility of the niche. This suggests, among others, the need forin-depth research in this area.

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Fig. 1 Source-wise distribution of typical fossil fuel derived energy supply in India (Adapted from TechnicalNote on Energy, Planning Commission, Govt. of India, 1998–1999)

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3 Advantages of algal biofuels

Green algae have been identified as a potential source of renewable biofuel since the 1960s(Oswald and Golueke 1960; Benemann et al. 1977). Algae comprising of both micro andmacro forms have the potential to generate significant quantities of biomass and oil (lipids)suitable for conversion to biodiesel and other fuels. Algal species have higher growth ratesunder natural conditions and higher biomass productivities compared to oil-seed crops interms of land area requirement. For example, most crop plants do not have adequate leaf areaor light harvesting capability for the first half of their crop life i.e. up to 45–60 d lightinterception by crop plants are less than 50 % (Lal et al. 1998, 1999). Algal growth can reachhigh densities to achieve greater levels of light harvest within a few days and are henceconsidered economic and efficient. They reduce net GHG emissions when used as replacementfor fossil fuels (Benemann and Oswald 1996; Sheehan et al. 1998; Huntley and Redalje 2007;Schenk et al. 2008; Chisti 2008; Rittmann 2008; Dismukes et al. 2008; Brune et al. 2009;Brennan and Owende 2010; Stephens et al. 2010) (Fig. 5).

Various biofuel feed stocks potentially available from algae are amenable for direct use ormay be processed further to gas or liquid biofuels by several bio-chemical and thermo-chemical processes (Rittmann 2008; Amin 2009; Demirbas 2009; Brennan and Owende2010). Harvested algae may also be dried and burnt for direct energy recovery (Kadam2002). A variety of thermo-chemical conversion methods have been visualized e.g. pyrolysis,gasification, liquefaction and hydrogenation of the algal biomass to yield oil/gas (liquid andgaseous) biofuels (McKendry 2002a, b; Miao and Wu 2004). Therefore much of the technologiesof fuel conversion from solid to liquid and solid-gas–liquid through various catalytic conversionscan also be applied to algal biofuels. The biochemical conversion processes include fermentationand anaerobic digestion of the algal biomass resulting in bio-ethanol/bio-`butanol, methane andbiohydrogen (McKendry 2002a, Melis 2002). Lipids (mainly Tri-Acyl-Glycols (TAG)) can beextracted and purified from algae and later transesterified to biodiesel (Miao and Wu 2006; Chisti

36%

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Coal Oil Gas Hydro NuclearFig. 3 Distribution energy sour-ces in the energy basket of India(Planning Commision of India,2006)

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Transport IndustryPlantation Power generationPrivate sales Miscellaneous services

Fig. 4 Sectoral energy use in In-dia (Planning Commission of In-dia, 2006)


2007; Hu et al. 1998). Biodiesel generation from algae is considered to have a higher oil productionpotential compared to oil seeds (Sheehan et al. 1998; Chisti 2007).

Cultivation of algae does not necessarily need prime agricultural land and can be grownunder desert like conditions using brackish and saline waters that are unfit for terrestrialcrops the water used for algal cultivation does not compete for agriculturally importantactivities (Fig. 6). Algae derived bio-fuels (ADBF) could thus be raised without obviousthreats to food security of the region. One such illustration that is often quoted is that usingonly 0.49 % of land area of USA, all its PDF needs could be met through raising algae andconverting it to ADBF. Similarly, the use of marine and salt tolerant algal species makescultivation in open seas possible without affecting food security issues of a land (Ben-Amotzand Avron 1983).

Research carried out with a broad purpose of sequestering large quantities of C (asmicroalgae that settle to the bottom of the ocean) by iron (Fe) and nutrient fertilization atthe sea surface has also triggered research on the possibilities to use micro and macro algaein various shallow seas as well as for algal biofuels (Smetacek and Nicol 2005) promisingalgal cultivation for biofuels with C-capture. Firstly, sequestering C generated from nearby

Fig. 5 A 1000 L raceway pond supporting the growth of various algae including Botryococcus mahabalispecies used at CFTRI, Mysore

Fig. 6 The dense algal (Euglenasp.) growth at the sewage treat-ment plant at Vidyaranyapuram,Mysore (India)


coal fired power plants provide both a low cost source of CO2 as well as to some degreeoffset cultivation costs (Borowitzka 1999). A lot of promise of improved strains andincreased lipid accumulation has emerged from research around the world making thispromise much more attractive (Chisti 2007; Chisti 2008; Ramachandra et al. 2009; Khanet al. 2009; Singh et al. 2011). Towards this direction much of the research here has beenfocused on screening oil rich algae and finding suitable growth conditions for greater oilyields (Hu et al. 2008; Griffiths and Harrison 2009). There has been a large extent of studiesto identify biochemical environments that trigger accumulations of neutral lipids such asTAGs in algal cells for example nutrient stress as N and P limitation (Li et al. 2008; Convertiet al. 2009; Rodolfi et al. 2009; Dean et al. 2010) and Fe limitation (Li et al. 2008) etc. Amajor limitation of this approach is the decreased biomass productivity of cells. Under suchconditions, in spite of high lipid yields the net lipid productivity is low when measured as glipid harvested/m2/d (Griffiths and Harrison 2009). Therefore, as a strategy it is suggested tohave higher biomass yield than high lipid content of algal cells (achieved usually byinducing stress conditions). Higher biomass yield can pave ways for other possible routesof energy generation using many other biofuels by employing various other bio-chemicalprocesses. As discussed later on in this article, India has significant area of ‘wasteland’ thatis believed to have the ‘potential’ for algal biofuel production.

4 The potential for sustainable algal biofuel production in India

One of the most prominent advantages of algae is their adaptability to grow in extremeconditions and even polluted environments. Even in nature they grow at high cell densitiesup to 107 cells/ml (Chow et al. 1999) in nutrient rich waters and therefore can be grown inconditions with minimal freshwater requirement compared other land-based biofuel crops.While growing in nutrient and organic rich polluted waters, algae are known to absorb largequantities of polluting plant nutrients and thereby strip the polluted waters off these commonpollutants. Many algae grow well in a variety of salt concentrations (halo-tolerant) and evendominate at higher salt concentrations (brackish waters; Rodolfi et al. 2009; Takagi et al.2006). Wastewaters are equally good options as feedstock for algal-products (algal biomassand algal biofuels). For a long time it is well known that microalgae are the key players inthe treatment of domestic wastewaters in oxidation ponds and ditches (popular in Indiantowns) where the growth and function of algae are poorly controlled. Algae have beendeployed and utilised for low-cost and environmentally friendly wastewater treatmentcompared to other more commonly used energy intensive treatment processes (de la Noueet al. 1992; Green et al. 1995; Oswald et al. 1957; Pittman et al. 2011; Woertz et al. 2009;Chinnasamy et al. 2010). Although these processes are algae dependent, algal biomass is notutilized economically.

In developing countries there is a growing consensus on the enormity of wastewatergeneration and at the same time the technologies available to treat them are expensive(Gasperi et al. 2008; discussed later). The N and P concentrations of municipal wastewatersof large metros of India range from 30–100 ppm and 10–45, respectively, (Chanakya et al.2006; Chanakya and Sharatchandra 2008; Mahapatra et al. 2011a); over 1000 ppm inagricultural wastewaters (de la Noue et al. 1992; Gonzalez et al. 1997; Wilkie and Mulbry2002) 12swine/piggery wastewaters (An et al. 2003). In India, in the past agricultural waste-waters rich in nutrients were almost always reused on land enabling nutrient recovery. Further,agricultural practices have become mechanized, market centric and labour cost sensitive,therefore smaller proportions of agricultural wastewater are recycled on the farms and most


of it is discharged, e.g. coffee pulping wastewater (Chanakya and de Alwis 2004; Chanakya etal. 2005). Algae being rapid assimilators of nutrients, they effectively grow in these nutrient richenvironments and therefore it makes them the most suitable candidates for sustainable and low-cost wastewater treatment (Hoffmann 1998; Mallick 2002; de-Bashan and Bashan 2010; Khanet al. 2009; Singh et al. 2011; Chinnasamy et al. 2010) with simultaneous algal biofuelgeneration potential (Benemann et al. 1977; Oswald and Golueke 1960). When grown in suchwastewaters, nutrients needs of the algae are available not merely at a low cost but quite oftenthe generator of wastewaters would pay a price for treating the wastewater. The nutrients wouldthen be available at a notionally negative price, at least for the present.

5 Algae cultivation systems under Indian conditions and their potential productivities

Cost effectiveness and better resilience have been the key characteristics of open pond basedalgal systems compared to photobioreactors. The open ponds are usually reported to bedominated by two to six species of microalgae with a range of evolutionary advantages;rapid growth, resistance to predators, tolerance to high levels of dissolved oxygen (Maeda etal. 1995). Open pond system is 10 times less expensive compared to photobioreactors(Sheehan et al. 1998). Raceways are characterized by low-cost and low productivitycompared to photobioreactors. In tropical countries such as India, photobioreactors needenergy intensive cooling and is avoided in open ponds. At water depths of 10–15 cm a totalbiomass of 1 g dry wt/L at a productivity of 60–100 mg/L/day has been reported (Pulz2001). When considering large scale cultivation microalgae can be cultivated in the flat plainregions and coastal areas of India. The open pond systems needs to be encouraged for algalbiomass culture to achieve high and sustained growth rates and oil yields essential for algal-based biofuels

Mass cultivation of algae in India dates back to race-way pond based cultivation ofSpirulina for food and essential metabolites (Venkataraman and Becker 1985; Venkatamaran1986). Studies involving the growth of the oilagenous algae Botryococcus mahabali inraceway ponds gave productivities of 1.0–1.5 g/L with total hydrocarbon content of 14 %(Dayananda et al. 2010), 9 g/m2/d (unpublished data), and also provided long chain fattyacids (C21-C23, Dayananda et al. 2006). In another case the fat content of 22 % (w/w) withpalmitic and oleic as major fatty acids (Dayananda et al. 2007b) has been achieved. Asynthetic media with 16:8 h light:dark cycle gave 33–46 % hydrocarbon (Dayananda et al.2007a). Optimum concentrations of di-hydrogen potassium phosphate, potassium nitrate,magnesium sulphate and ferric citrate increase biomass up to 0.65 g/L with 50.6 % (w/w)hydrocarbon in 30 d (Dayananda et al. 2005). The studies from the wastewater treatmentsystems in Mysore and Bangalore reveal biomass productivities of 9.15–12.6 g/m2/d(unpublished CST, study).

In the case of marine algae, commercial cultivation of a macrophyte, Kappaphacusalvarezii, originated in Philippines in 1960 (Doty and Alvarez 1975). Since then countriessuch as Japan, Indonesia, Tanzania, Fiji, Kiribati, Hawaii and South Africa cultivate thisspecies on large scale (Rao et al. 2008). In India cultivation of this seaweed was initiated atMandapam in South Eastern India (Eswaran et al. 2002). It is increasingly being cultivatedaround Rameshwaram providing up to 30 g/m2/d (Sea6, per. Comm.; locally called PepsiPaasi). A few experiments on cultivation of K alvarezi in tidal pools were carried out atOkha during 1994–95 (Mairh et al. 1995) and Rao et al. (2008) attempted to cultivate thisseaweed in the open sea at three localities viz. Mithapur, Okha and Beyt Dwarka and weresuccessful. Saltwater cultivation of macro-algae has also been focused on products such as


carrageenan, etc. and fetches a high price (Vijayalakshmi 2003; Krishnamurthy 2005) andhas a large extent of useful fatty acids (Fayaz et al. 2005).

6 Sustainability issues of extensive algal biofuel cultivation

The sustainability of extensive algal cultivation for biofuel in this case is challenged byseveral factors and the important ones are as follows.

a. Access to and availability of land for algae cultivationb. Water sources of algal cultivationc. Nutrient sources and supplyd. Secondary wastes and environmental impacts pollutants and other wastes

6.1 Access to and availability of land for algae cultivation

In most of the developing countries availability of cultivable land for alternative uses are lowand generally have a lot of competing uses. This is also true for wastelands where land is‘wasted’ either because of extreme levels of soil erosion or because of a hostile and arid climate.A lot of earlier research of the cultivation of woody biomass on wastelands indicates that out ofa total land area of 328 Mha about 160 million is under the plough for field crops and about60 Mha form various types of potentially “usable” wastelands (Planning Commission 1998).Further, as shown later on, much of these wastelands generally occur in areas where theprecipitation is poor and there are usually no sources of non-agricultural water, as has beenvisualized for other countries, e.g. US (Savage 2011). This suggests that it is required that croplands that can support algal cultivation needs to be used in the same manner and strategy as isdone in multiple cropping or multi-tier cropping to enable the same land to be used both for cropgrowth as well as for algal cultivation while ensuring that they do not compete with each otherand conflict sustainability goals. This option is discussed below.

A large tract of land in the Rann of Kutch area (about 3 Mha) occurs as a highly salineland with sparse population and highly sodic soils where the ground water, due to geologicalreasons, is more saline than seawater (Dhargalkar and Untwale 1991). Much of these landsare flat, lie at low altitudes above sea level, and therefore make excellent low cost and non-competitive land resource on which algal biomass could be grown without causing anythreat to food security. A small part of this land is already used in salt manufacture wherehighly saline ground water is evaporated to make salt. The land is generally unfit to supportgeneral crops. Almost all of this 3 Mha is therefore potentially available throughout the yearfor algal cultivation using seawater. Several halotolerant species have been observed to havehigh lipid accumulation and biomass productivity (Rodolfi et al. 2009). These species can begrown in non-arable and wastelands by pumping saline water either from the sea or thatpresent below ground as ground water. Many marine species have been screened for theirlipid content and lipid productivities. Species such as Nannochloropsis and Tetreselmis werefound highly promising (Rodolfi et al. 2009). In a comparative study of freshwater andmarine algae, it was observed that the lipid content of marine algal species was around 24and 28 % for N-deficient and N-replete cultures, respectively (Griffiths and Harrison 2009).These had an average doubling time of 19 h (μ, specific. growth rate00.88/d). Among themarine algae the most productive strains were the Tetraselmis suecica with lipid productivity99 mg/l/d, biomass productivity 0.59 mg/l/d, lipid content of 17 % followed by


Nannochloropsis salina with lipid productivity 82 mg/l/d, biomass productivity 0.27 mg/l/d,lipid content of 31 % followed by Nannochloris sp. with lipid productivity 77 mg/l/d,biomass productivity 0.23 mg/l/d, lipid content of 28 % followed by Pavlova lutheri withlipid productivity 75 mg/l/d, biomass productivity 0.31 mg/l/d, lipid content of 36 % followedby Phaeodactylum tricornutumwith lipid productivity 72 mg/L biomass productivity 0.34 mg/l/d, lipid content of 26 % (Ackman et al. 1968; Parrish and Wangersky 1987; Sukenik et al.1993; Hu and Gao 2003; Griffiths and Harrison 2009). Although adequate data for Indianspecies does not exist, it appears that the marine algae in sodic lands is a good option –especially for an area such as Kachch, Gujarat, Western India.

India has a very large area of land under flooded paddy cultivation. Out of about 42 Mha ofland under paddy cultivation, nearly half of it is under flooded irrigation method of cultivatingpaddy crop (Table 1). It is difficult to generalize, area wise, the practice of and the extent ofwater held on the land for paddy crop cultivation (flooding or non-flooding type). This variessignificantly within a region and even a village. However, three to four types of cultivationpractices are possible – rainfed upland, rainfed with partial flooding, irrigated with constantflooding and deep water paddy. Only the last two types have a sensible potential to raise asimultaneous algal crop. Further, only irrigated paddy with constant flooding makes currenteconomic sense to raise a simultaneous algal crop because it is possible to raise algae for about30–60 d giving at least 4–8 simple cycles of algal harvest (at 7 d intervals). The zones of India,its states and districts of Karnataka state where flooded irrigation is practiced for paddycultivation are presented in Fig. 7 and Table 1 along with the total cultivated area.

In most areas of flooded paddy cultivation, land is flooded well before the paddy crop isplanted and also from the time of transplanting the paddy seedling to about the 45–60th day(age of crop) the vegetation is sparse and much of the water surface is open to sky – i.e. theleaf area covering the land area Leaf Area Index (LAI) is still quite low as seedlings are stillsmall. It is well known that up to the 60th day, light interception by the paddy plant is lessthan 50 % of the solar radiation. Thus, since a lot of incident sunlight falls on water surface,it is potentially possible to grow various species of algae during the early part of the paddycrop and rapidly harvest them for local extraction of algal crude, biogas and recycling ofnutrients back to the soil of the current paddy crop. In this way, algae can be cultivatedwithout interfering with the crop growth and the same piece of paddy land could be used‘twice’ without interference with the main crop. In low land areas of paddy cultivation, inlands that receive runoff from paddy lands upstream, algal growth is often very high. Thesealgae are often considered ‘weeds’ that ‘eat’ into the nutrition provided for the crop plant e.g.delta area of Kaveri or Krishna rivers in the east coast (Roger et al. 1985). Thus under suchcircumstances, when algae is cultivated only for the first 60 days of crop life, there is apotential for nearly 16–18 Mha for algae cultivation area wherein cultivation is possible for

Table 1 Region-wise potential for flooded paddy and consequent simultaneous algal cultivation underflooded paddy conditions

Region / State Total area Continuouslyflooded paddy

Intermittentlyflooded paddy

Deepwaterpaddy

Uplandpaddy

Eastern Region 18.583 5.694 8.610 1.639 2.640

Southern Region 7.987 5.070 1.892 0.24 0.785

Northern Region 8.277 3.991 3.174 0.233 0.879

Western Region 7.385 1.742 3.652 0.322 1.669

Total 42.232 16.497 17.328 2.434 5.97


2 months (Fig. 7, Tables 1 and 2). This period of 60 d algal growth on 18 Mha could, forpurposes of calculation, be equated to about 3 Mha equivalent of year round cultivation ofalgae.

A large part of the shallow seas around the coast line are also potential areas forcultivation of the larger macro-algae. In many areas these form a rich fishery and aretherefore not suitable for algal cultivation. On the other hand, due to various reasonssuch as over-fishing, the fish catch in a large part of the shallow seas on the easterncoastline of India is very low and is no longer economic to fish. These areas are quitesuitable for cultivation of macro-algae. The fisher-folk who are in debt due to lowcatch have now switched to cultivation of anchored macro-algae (Chanakya et al.2012) Although macro-algae such as sargassum, Kappaphacus, etc. do not have highlipid content, they could still provide a substantial quantity of biogas (energy) uponanaerobic fermentation as well as a host of economically useful by-products. Biogas isproduced from the unused and wasted portions and nutrients returned to the farmedareas to ensure sustainability. There is however, very little estimate of this potentialgeographical area and yields of macro-algae. Considering the vast coastline (about4000 km) and the continental shelf, an area of another 3 Mha could be assumed asavailable of algal cultivation (75 % of 4000 km coastline up to 10 km).

0 – 10 %

10 – 30 %

30 – 60 %

Above 60%

Fig. 7 State-wise distribution of irrigated (flooded) paddy in India (in Mha, insertions). The inset map of theState of Karnataka shows the district-wise irrigated area under flooded paddy conditions. The numeralsinserted in the districts suggest ‘000 ha of land under flooded paddy cultivation in each of the districts. Thuswe see that a large part South and Eastern India is suitable for algal cultivation in this mode


6.2 Water sources for algal cultivation

One of the simplest methods of cultivation would be through open water ponds – on the sea orland. Open water surfaces lose large quantities of water (total daily evaporation, measured inmm/d) that could range between 5 mm in rainy andwinter months in India and around 10mm/don a hot summer day (Central Water Commission 2006). Considering that India in general has awater deficit budget where the total evaporation possible in a year generally exceeds the annualrainfall, the different regions in India have a varying degree of aridity. Second, as most of theuseful and nearly flat land is already cultivated, a potential option to cultivate algae on the samefarmed land can be realized only after a crop is grown – even if there is a hope for surplus waterin the region. In this way algal cultivation need not be done instead of a food crop and threatenthe food security of the region. Various parts of the country could then be divided into zoneswhere there is more than 150 d of acceptable water balance (90–120 d crop+30–60 d algalcultivation), 150–210 d (30–60 d algae), 210–270 (two agricultural crops or one field crop+90 d algae cultivation) and finally locations with >270 d of positive water balance. Figure 8shows potential areas where there is a likelihood of surplus of water after cultivating a normalfield crop. As the north east and the northern Himalayan regions are mountainous, they are notincluded in the projection. For the rest of the country, only a small part of the geographical area -the dark hatched area and the dark blue areas have the potential climate to cultivate algae in theopen using natural water sources that may be collected in the area. In this projection we attemptto show that when we cultivate algae in these zones, the added water burden of evaporation ofwater from open algal ponds will not lead to water deficit conditions (water security) andtherefore make the overall process unsustainable. Greater effort is however, required tosegregate the overlapped paddy area and potentially wet area indicated above and is thereforenot included in the mitigation potential estimates.

6.3 Nutrient sources and supply

Algae like most crop plants require plant nutrients such as N,P,K and other micro nutrients.Earlier research suggests that between 0.3 and 0.5 kg N, 0.1 kg P and 0.1 kgK are requiredfor producing 1 kg algal biofuel (lipid;). The annual crude oil consumption has beenincreasing gradually from about 90 Mtoe (1998) to about 156 Mtoe (2010; Figs. 1 and 2,only transport fuel considered). Assuming a need for an annual requirement 160 Mtoe algalcrude, the fertilizer required for producing algal biofuels would be 80, 16 and 16 Mt of N, Pand K, respectively. Even if we consider that the fertilizer use efficiency would be as high as50 %, the annual additional NPK needs at the national level would be 160, 32 and 32 Mt ofNPK. This would greatly burden the already high level of fossil fuel dependence for N andother fertilizers in India. Other sustainable alternatives need to be found.

Several blue-green algae and green algae have been cultivated in paddy fields in the pastlargely to raise the N content of the system (Singh and Singh 1987; Singh 1981, 1982,1985). It is generally reported that up to 40 kg N/ha could be fixed by these algae and Azolla(Singh and Singh 1987). The most successful strategy was to feed the algae/Azolla with P anda small quantity of N when these were inoculated into the paddy land (Bisoyi and Singh 1988).Azolla or blue green algae grew till about 60 d of crop life after which they became shaded.These algae were then trampled and pushed back into the soil where they decomposed rapidlyto provide nutrients to the reigning paddy crop. The key strategy was that the P and K and someN needed for the paddy crop was provided to the Azolla. This in turn grew and when trampledand pushed back into soil around the 60th day of the paddy crop, it released the ‘locked’nutrients to the paddy crop later on. This strategy greatly reduced the N needed because the


moderately decomposing Azolla ensured most of the released nutrients were picked up by thepaddy crop in the very same way as slow release fertilizers. This reduced the potential lossesthat would have arisen from the use of urea (>75 %N lost, Chanakya and Sharatchandra 2008).The very same strategy and practices now needs to be adopted to raise algae on paddy landssuch that no additional nutrients need to be provided for raising algae. However, the energycontent of algae is recovered before it is to be sent for fertilization.

7 Algae in domestic wastewaters

Urban and peri-urban domestic wastewaters in developing countries have been considered to bea large source of plant nutrients that on the one hand enters traditional water bodies and causeseutrophication and water pollution and on the other hand it disables the water body from

< 150d

150-210 days

210-270 days

Fig. 8 Wet regions of India where algal cultivation is technically feasible in terms of adequate availability/supply of water after meeting a single or double crop is determined as a function of the period for which thecumulative open pan evaporation (OPE) is less than the total annual precipitation measured in days


carrying out its normal ecological functions (Chanakya et al. 2006; Chanakya and Sharatchandra2008; Mahapatra et al. 2011a, b, c). This is largely because cities are rapidly urbanizing andmunicipal bodies are generally unable to cope up with the requirements for treating wastewaters(Mahapatra et al. 2011a). Much of the wastewater and partially treated wastewater then flowsalong water courses to reach traditional water harvesting tanks in the upland or other watercourses nearby in lowlands (Mahapatra et al. 2011c). According to the recent reports of theCentral Pollution Control Board (CPCB) the waste water generation in the country around 40billion litres per day mostly from urban areas and about 20–30 % of the generated wastewaterreceives treatment for C removal. Hardly any of the treatment plants carry out removal of the Nand P nutrients from wastewaters. Further, most of the houses in emerging urban areas generallyuse soak pits and therefore only a fraction of the sewage generated flows out of towns and cities insewage channels (Chanakya and Sharatchandra 2008). However, when urbanizing areas developand become dense, most of them become connected to underground sewage lines and therefore itis appropriate to assume that in the near future all the sewage generated will flow out of the cityand will require treatment for 100 % of this discharge capacity (Table 3).

The per capita water supply in India is 188.73 (measured as liters per capita per day, lpcd,CPCB 2011) and sewage generation is 138 lpcd indicating the enormity of the source. Whenwe account for all the losses between sewage generation at the household and to the pointwhere it reaches the treatment plants: losses due to evaporation, seepage in open unlinedchannels and infiltration into the ground, around 80 lpcd of sewage reaches various types ofreceiving water-bodies causing pollution and eutrophication. There is potential to reversethis situation by growing various algae in these wastewaters. Sewage degrading anaerobicallyin water bodies generates methane. Assuming a daily discharge of 0.06 kg (dry) per capita,350 L biogas potential/kg waste, 60 % methane in biogas and 80 % conversion efficiency thiswould lead to a daily methane generation of 10.3 g methane per capita. In order to account forother wastes, especially from the kitchen and bathrooms, entering sewage, the abovebiochemical methane potential (BMP) from the BOD level (250 mg/L, 80lpcd) dischargedthe estimated methane generation in sewage systems would be similar (9.6 g CH4/cap/d).

When algae are grown on such wastewaters, firstly this avoids the methane likely to begenerated because algae (and bacteria) consume the decomposable matter instead and no

Table 2 Estimation of land area available for the cultivation of various types of algae and the potential algaland biofuel yields from various cultivation options. (Superscripts #1-Paddy land area of 18 Mha with potentialof about 2 month cultivation is annualized to 3 Ma equivalent of round the year cultivation, #2-is a large salineaffected land and close to the sea and is therefore possible to raise salt tolerant algae,-#3-Coastal areas wheresea depth is up to 5 m and fishery is poor, 4-backwaters in various coastal areas where water is usually saline/brackish and 5. Urban wastewater, predominantly sewage with 40–60 mg/L N and 8–20 mg/L P etc

No. Location Potentialcultivationarea (Mha)

Potentialproductivity(low, t/hayr)

Potentialproductivity(high, t/ha/yr)

Potentialproductivity(avg, t/ha/yr)

AlgalCrude(Mtoe/yr)

By-productMtoe

Totalyields(Mtoe/yr)

1 Paddy land1 3.0 30 75 45 27 43 60

2 Kachch2 3.0 30 60 45 27 43 60

3 Sea Shelf3 3.0 10 NA 10 - - -

4 Back waters 2.1 15 NA 10 - - -

5 Urban wastewater (asbillion m3)

60 10–15 NA 10 0.36 0.43 0.79

Total 9.0 54.36 86.43 120.8


methane is released. Algal systems are being practised in wastewater treatment eitherthrough the use of stabilisation (oxidation) pond based systems and recently shallowwell-mixed suspended algal raceway type oxidation ponds with mechanical mixing (Greenet al. 1995; Hoffmann 1998). As organic matter within sewage decomposes and is consumedby algae and bacteria, a lot of surplus nutrients are released such as N~40 mg/L and P~5–20 mg/L (Mahapatra et al. 2011a). The algal communities in sewage fed water bodies inBangalore have been reported to be responsible for 76 %N and 60 %C removal and evenhigher at other locations (Gonzalez et al. 1997; Masseret et al. 2000; Aslan and Kapdan2006; Ruiz-Marin et al. 2010; Mahapatra et al. 2011a). Algae are efficient in removing N, P,organic toxicants and toxic metals from wastewater (Mallick 2002; Ahluwalia and Goyal2007) and hence are key players for nutrient remediation particularly during the secondary andtertiary treatment phases of wastewater. These nutrients stimulate a fresh growth of algae andfrom this additional algal biomass can be raised such that most of the nutrients are removedfrom the water and water is purified for further use. In this way, 0.06–0.2 g dry algae/l/d or 10 gdry algae/m2/d (depending upon the depth) can be harvested from sewage ponds. Figure 6shows the dense green algal growth in a sewage treatment plant in South India.

The current potential of algal biomass and therefore algal biofuel from wastewater isillustrated from a study carried out on the lakes of Bangalore (Karnataka state). Partiallytreated sewage, about 500 million liters per day (MLD), flows into two cascading man-madewater bodies Bellandur and Varthur lakes located in the Southeast of greater Bangalore region,Karnataka state, India. This is illustrated in Fig. 9. Partially treated sewage enters BellandurLake first at a carbon, nitrogen and phosphorous (CNP) load of 110, 80 and 30 ppm (respec-tively) and exits the Bellandur Lake with more than 50 % reduction in load along with a largegrowth of micro-algae. Sewage flowing through Bellandur Lake has an estimated residencetime of about 7 d. The community assemblage of algae varies with season. The outlet of thislake feeds into a second water body, the Varthur Lake, with a residence time of 5.5 d and exitsthis lake with a further 50 % reduction in CNP loads. The density of naturally growing algae ishigh (> million cells/mL) and corresponds to an estimated 10 g/m2/d growth rates (at times itcan reach up to 24 g/m2/d, unpublished field data) although the lipid content is not veryhigh. This 365 ha water body, Bellandur Lake, is estimated to yield about 13,000 t algalbiomass/annum. Out of this, assuming only 40 % is harvestable through natural extrac-tion processes; it still yields ~5000 t algal biomass/yr. With current cultivation practices

Table 3 The magnitude of wastewater generation from various sizes of towns and cities in India (CPCB2006)

City types Populationsize

No. ofcities

Wastewatergeneration(MLD)

Treatment plant(Installed capacity, MLD)

%ageTreatment

Metropolitan cities >10 Lakhs* 35 15,644.0 8040 50 %

Class-I cities1 >1 Lakh 498 35,558.12 11553.68 32 %

Class-II cities2 10, 000 to 1lakh

410 2,696.2 233.7 10 %

Cities at Ganga Basin3 20 million 113 2,637.7 1174.4 44.2 %

Total 56,538.0

*Lakh generally refers to 100,00000.1 million. In the Indian classification of towns and cities,

1 - Class I cities (cities with Population >1, 00,000)

2 - Class II cities (cities with Population 10,000–1, 00,000)

3 - Ganga Basin - Population living around Ganga river basin in the north and north-eastern parts of India


and an average ‘potential’ lipid content of 20 % this is estimated to provide a potential of1000 t of algal lipid (crude) from this water body annually. It is therefore anticipated thatwith improved strains and harvesting techniques the algal biofuel extractable becomesmuch more attractive. At present this system avoids a treatment cost of about Rs (IndianRupees) 2.5 Million/d (@Rs5/kL) and has the potential to generate 1000 toe algal crude/yr; recovers plant nutrients (40 tpd N, 15 tpd P) and the residue (after oil extraction) willstill have an energy potential of 1600 toe as direct combustion of residual algae or1200 toe as biogas (@75 % decomposability). Thus from each open sewage treatmentalgal pond, it is possible to extract 2200 toe of algal biofuel totalling about 6600 t for a500 MLD input of sewage. Thus for a country level efficient re-use of wastewater by analgal biofuel pond based treatment system it will be possible to generate about 0.8 Mtoeof algal biofuels. Such an effort not only enables domestic wastewater to be put to gooduse but also enables rapid reuse of wastewater, which is often the need in a developingcountry situation. The recovery of plant nutrients for reuse in crop systems is anotherimportant bonus not accounted for in the energetic or mitigation calculations.

An illustration of the potential options for algal cultivation in flooded paddy fields is shownin Fig. 10. Algal biomass can be transformed to biofuels through a wide range of technologiesstarting from direct burning, biomethanation, briquetting, lipid extraction coupled with bio-methanation etc. However, lipid extraction from algal biomass as a feedstock for biodieselproduction will be by far themost promising option, particularly when there exists cogenerationof methane from the residual algal biomass remaining after lipid extraction (Brune et al. 2009)and is coupled to the return of nutrients in algal mass to paddy soils ensuring high nutrient useefficiency by the crop system and overall sustainability. Simple and energy efficient technol-ogies for algal harvest at farm and village scales are not available as of today. However, it issuggested that algal species that tend to float up during afternoon or those that settle at night (orboth) are good traits that can be used to transfer the algal mass into a settling pond and create alow energy algae harvest system. Algal biomass concentrated thus could be sent for villagelevel extraction and biodiesel production. The residual non-lipid mass could then be used formethane production and returned to paddy crop production for nutrient recovery. In this way, aswas done in the past with Azolla, plant nutrients designated for the paddy crop is only‘borrowed from the next crop’ for use by the current algal crop and returned to the paddy cropin time to realize normal paddy yields. In this way no additional fertilizers need to be used.

8 Mitigation potential in India

The mitigation potential of algal biofuel production has not been estimated with sufficientclarity/accuracy for India because locations where these algal biofuels can be raised and

Fig. 9 Nutrient flow across the urban lake gradient and consequent potential for energy capture


possible biofuel applications are still not well established and therefore can only bedetermined for various possible scenarios emerging from cultivation options and relatedtechnologies. The mitigation potential as discussed earlier in the paper emerges in threemajor streams, namely,

a. Avoidance of GHG emissions from normal practices of wastewater treatment and paddycultivation by simultaneous algae cultivation

b. From C-capture opportunities in the vicinity of C-producing industries and utilities(captured in algae)

c. From the production of alternative fuel streams

8.1 Avoidance of GHG emission practices by simultaneous algal cultivation

A switch over to algae based wastewater treatment system instead of the conventional systemsthat emit methane would bring about a large reduction in methane emissions. Because is algaegrown in sunlight and they photosynthesize, algae prevent the growth of anaerobic (oxygenintolerant) methanogenic bacteria while simultaneously reducing the smell of decomposingsewage. The daily discharge of domestic wastewater is 56.5 billion liters/day and for includingfuture growth it is rounded to 60 billion liters per day. For an estimated 60 billion liters per daysewage, the expected biogas production (@200 L biogas/kL sewage) would be 12Mm3 biogas/d (0.00514 Mt methane and 0.108 Mt CO2 equivalent per day or 39.4 Mt CO2 per annum).However, not all the sewage is expected to be collected on a daily basis and many of the septictank systems are expected to survive urban development efforts and sanitation measures.Therefore taking only 60 % of urban households would be connected to sewage flow systemsthe mitigation potential would be around 23.7 Mt CO2/annum.

A similar situation is expected to happen in paddy lands. With intense algal cultivation inflooded paddy soil, the pH would rise to high levels (>8.5) and oxygen (O) content of water isexpected to be supersaturated at mid-day (>12 mg/L). Such highly O rich conditions of the waterduring the day are not conducive for methane producing organisms to thrive. Although at night,in the absence of O being added to the water by algal photosynthesis, the O levels would fall, thiscyclic oxygenation would inhibit methane emissions from paddy fields because O is toxic tomethanogens and methanogens grow very slowly. In a situation where high intensity algalcultivation is carried out in paddy fields methanogenesis and therefore methane emissions frompaddy soils are not expected to occur. In the past, the methane (CH4) efflux in planted plotsvaried with the rice variety and growth stage and ranged from 4–26 mg/h/m2 (Adhya et al. 1994,2000). From an area of 18 Mha emitting between 4 and 26 mg/h/m2 86.4–561.6 kg CH4/ha incrop cycle of 90 d, the net CH4 emissions avoided and its mitigation potential is between 0.259and 1.68 Mt CH4 or 5.4–35.3 Mt CO2e.

Fig. 10 Schematic diagram of proposed algal cultivation in paddy fields for biofuel production


8.2 Mitigation from C-capture opportunities in the vicinity of C-producing industriesand utilities

Much of the power generation utilities in India are coal based and therefore generate largevolumes of fossil fuel derived CO2. A temporary C capture in a chemically driven systemthat later releases CO2 to wastewater growing algae can significantly increase the C captureand simultaneously produce algal biofuels. All coal based power plants maintain large ashponds that are covered by a layer of water that are generally alkaline with high solidscontent. While this is favourable for a few algal species, the ability to dissolve CO2 inalkaline waters is unfavourable. This is a large potential for algal cultivation and C-capturewhose magnitude and feasibility has not been examined significantly for India and thereforeneeds further research. Many of the power plants, because of their need to use largequantities of coolant water are situated close to water bodies. Some of the newer ones havealso come up near the sea shore using seawater as coolant water. These provide immenseCO2 fertilization potential leading to production of algal biofuels.

8.3 Algal biofuels at alternative locations and from the production of alternative fuel streams

Algal biofuels are expected to provide a decentralized production of algal crude (lipids) thatare capable of being converted to biodiesel and similar fuels addressing to a large extent thetransport fuel needs. The total algal crude production is estimated based on the currentpotential for cultivation of algae providing about 15 g dry matter/m2/d and with a lipidcontent of 20 %. At this scale of production and the current level of technology the overallalgal crude production possible is about 54 Mtoe annually and can meet only about half thecurrent transport fuel needs. The conversion of oil extraction residue to methane or similarfuels is expected to generate another 86 Mtoe as biogas most suited for stationary engines orcompressed as natural gas equivalents. These values of yields are from the field and undergood cultivation practices. However, as algal strains and cultivation technology improvesthis level could be increased significantly and is a key area for further research.

9 Mitigation and adaptation linkages

Climate change induced impacts and outcomes to the habitable living environments arelikely to occur over a period of time. The solutions to such changes can be either by theadopting proper mitigative measures or adapting to it. The mitigative measures are enhanc-ing C traps, reduction in GHG emissions, switching to green renewable, increasing vegeta-tive cover, C sink in soils etc. (IPCC 2007). However adaptation to the changing climate canbe explained as adjustment in natural or human systems in response to actual or expectedclimatic stimuli or their effects, which moderates harm or exploits beneficial opportunities(IPCC 2001). The adaptations can be possibly anticipatory or upon encountering changes(reactive). Adaptation is essential to survive and has been known for ages.

Production and use of algal biofuel would represent a sustainable mitigation option - inthe production and switch to algal biofuels that is likely to occur later on, there are bothmitigation and adaptation components. As discussed earlier in the paper the mitigationpotential is reasonably large and can substitute up to 50 % of the current use of petro-fuels using the current state of art in natural algal cultivation and what is known aboutconverting algal crude to biofuels. Growing algae in flooded paddy lands will not only leadto GHG emission avoidance (mitigation) but will also enhance livelihoods in rural areas by


making agriculture more remunerative and therefore reducing pressure of outmigration fromvillages. Much of this algal biofuel production technology using freshwater and paddy fieldswill need a lot of socio-economic incentives to be created.

Some of the immediately needed mitigation and adaptation strategies will be

a. Currently, there is very little technology standardization at the decentralizedvillage scale where flooded paddy based algal biofuel will be produced andadapted to raising algal biofuels under paddy conditions as well as under highsaline conditions of Kachch and India’s backwaters. Unless these technologies aresimplified and made available in villages, this process will not succeed and cannotbe adopted on a large scale.

b. The sustainability of algal biofuels in paddy or in saline waters require the following

i. Algae need to be harvested by simple means and with resources accessible topaddy farmers – technology for this decentralized harvesting need to be developedand be adapted

ii. Harvested algae needs to be quickly extracted for algal crude and algal crudepreserved at the village level before cracking for ABDF

iii. Ancillary technologies to process algal extract residues to methane and nutrientsneed to be ready at village scale. Such adaptation needs to be carried out foroperation at village scale

iv. Nutrients locked in algal biomass needs to be extracted and returned rapidly to farmsso that it can be returned to the paddy crop in the fields with very short cycle time inorder to enable very little nutrient starvation for the paddy crop and yields are notaffected

v. Algal crude and biomethane collection and processing systems need to be madeready at rural nodes so that the crude cracking to ABDF is carried out at economicscales of operation and biomethane is collected in a gas grid in a decentralizedmanner.

vi. To use Kachch as a location for algal biofuel production, there is a need toconsider new land use options for Kachch with appropriate changes in landuse guidelines.

vii. Cultivation of algae in domestic wastewater, its harvest and algal crude andby-product production will not be readily acceptable under laws governing waste-water treatment. Many changes in guidelines will be required.

ix. Use of algal biofuels in commonly used engines is yet to be standardized andappropriate laws governing transport fuel production, storage, distribution and usein machinery still needs to be enacted. A Successful switch to algal biofuels is notpossible without such standardization and administrative facilitation.

x. Algal fuels need to be compatible with current engines or else adaptation kit needsto be developed and extensively marketed

xi. The use and preference for algal biofuels need to be incentivized in many ways tomake it popular and rapidly overcome the barriers to change

10 Conclusions

The study highlights the possibility of algal cultivation and availability of land and resources forbiofuel generation and discusses its technical feasibility in corroboration with agricultural systems


at decentralized levels. One of the key issues of algal biofuels in India is firstly the availability ofland, water and nutrient resources to primarily cultivate algae.

& To overcome this, algae can be grown as a multi-tier crop that temporarily borrowsnutrients allocated to the main paddy crop and all algae is harvested and returned to soilvery rapidly within the crop cycle. This creates a new concept of sustainability of multi-tier,multi-cyclic cropping.

& Two large-scale streams possible are cultivation in flooded paddy when the plants aresmall and the other is in saline affected lands in many parts of India of which the Kachcharea is the single largest block.

& Mitigation potential can reach over 50 % of the current use and with improvement intechnologies; it can reach higher levels of PDF substitution.

& As various technologies involved in the overall process is still nascent, it is expected thatthere will be a few barriers to large scale adoption.

& Technologies generated needs to be decentralized and remain functional at a rural scalewhere most of the land to cultivate algae exists.

& Adaptation needs will be smaller in the use of algal biofuels and is likely to be more inrapid with respect to absorption of the production technologies.

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Algal biofuel production and mitigation potential in India