Prospects and Po­ten­tial of Value Added Prod­ucts from a Biore­fin­ery

Gan­gagni Rao Anupoju, Sameena Begum, Su­dar­shan Jun­tu­pally, Vi­jay­alak­shmi Arelli, IICT- Hy­der­abad.

Chemical Industry Digest - - What’s In? -

As petrobased feed­stocks are fi­nite and di­min­ish­ing, bio-based re­new­ables are in­creas­ing in im­por­tance. Biore­finer­ies can pro­duce a va­ri­ety of prod­ucts. Biore­finer­ies could be­come a ma­jor con­trib­u­tor to the bio-based econ­omy of the na­tion, ac­cord­ing to the au­thor.

Ab­stract In the long run fos­sil based raw-ma­te­ri­als will de­plete and there­fore the shift to re­new­able based feed­stocks need to be ex­pe­dited [ 1]. This is also re­quired from the per­spec­tive of mov­ing to­wards a low car­bon econ­omy. Ex­ploita­tion of biomass, or­ganic waste ma­te­ri­als as re­new­able feed­stock is an at­trac­tive pos­si­bil­ity. The coun­try could prof­itably uti­lize 65% of the waste in pro­duc­ing en­ergy and value-added prod­ucts. This ar­ti­cle de­scribes biore­finer­ies, re­new­able feed­stocks and the mul­ti­ple prod­ucts that can be ob­tained from the biore­finer­ies which could con­trib­ute to the bio-based econ­omy of the na­tion.

Dr A. Gan­gagni Rao is Chief Sci­en­tist at Bio­engi­neer­ing and En­vi­ron­men­tal Sciences (BEES) Group of Cen­tre for En­vi­ron­men­tal En­gi­neer­ing & Fos­sil Fuels (CEEFF) divi­sion of CSIR-IICT, Hy­der­abad. He has about 25 years of re­search ex­pe­ri­ence in the field of waste man­age­ment and has his ex­per­tise in biometha­na­tion (anaer­o­bic diges­tion) and bi­o­log­i­cal gas pu­rifi­ca­tion. He has de­vel­oped a novel high rate biometha­na­tion re­ac­tor for the treat­ment of waste and retro­fit­ted nu­mer­ous bio­gas plants. He has 50 re­search pub­li­ca­tions and 4 patents to his credit.

Sameena Begum (BTech-Chem Engg – Ra­jiv Gandhi Univ) is cur­rently en­rolled for Ph.D in Chem­i­cal En­gi­neer­ing at Royal Mel­bourne In­sti­tute of Tech­nol­ogy (RMIT), Aus­tralia in col­lab­o­ra­tion with CSIR-IICT, Hy­der­abad. She is cur­rently pur­su­ing her doc­toral stud­ies un­der the guid­ance of Dr. A. Gan­gagni Rao.

Sud­har­shan Jun­tu­pally, post grad­u­ate in Mi­cro­bi­ol­ogy from Jawa­har­lal Nehru Tech­no­log­i­cal Univer­sity (JNTU), Hy­der­abad, is cur­rently pur­su­ing his Ph.Din life sciences un­der the guid­ance of Dr. A. Gan­gagni Rao at Bio­engi­neer­ing and En­vi­ron­men­tal Sciences Group of CEEFF, CSIRIICT,Hy­der­abad.

Vi­jay­alak­shmi Arelli ob­tained her Masters de­gree in Chem­i­cal En­gi­neer­ing from Os­ma­nia Univer­sity, Hy­der­abad. She is cur­rently pur­su­ing her Ph.D un­der the guid­ance of Dr. A. Gan­gag­niRao at Bio­engi­neer­ing and en­vi­ron­men­tal sciences divi­sion of CSIR-IICT, Hy­der­abad.

What is a Bio-re­fin­ery?

The biore­fin­ery is ex­actly anal­o­gous to a petro­chem­i­cal re­fin­ery. The only dif­fer­ence be­tween a bio-re­fin­ery and a pe­tro­leum re­fin­ery is the use of raw ma­te­ri­als[ 2]. In the pe­tro­leum re­fin­ery, crude oil and nat­u­ral gas is used as raw ma­te­rial whereas in the bio-re­fin­ery or­ganic waste and biomass is used as raw ma­te­rial (Fig.1). Among sev­eral def­i­ni­tions of biore­fin­ery, the most ex­haus­tive was re­cently for­mu­lated by In­ter­na­tional En­ergy Agency (IEA) Bioen­ergy Task 42. “Bio-re­fin­ing is the sus­tain­able pro­cess­ing of biomass into a spec­trum of mar­ketable prod­ucts and en­ergy”[ 3]. The bio-re­fin­ery is now a rec­og­nized ap­proach for trans­form­ing re­new­able raw ma­te­ri­als into sep­a­rate bio-based mar­ketable chem­i­cals and fuels. Biore­finer­ies can pro­duce both the en­er­getic and non-en­er­getic prod­ucts and can be broadly clas­si­fied into two main classes such as En­ergy-Driven Bio-re­fin­ery (EDB) sys­tems and Ma­te­rial Driven Bio-re­fin­ery (MDB) sys­tems[ 4]. In the EDB, the biomass is pri­mar­ily ex­ploited for the pro­duc­tion of sec­ondary en­ergy car­ri­ers such as trans­porta­tion bio­fu­els, power, heat etc., prod­ucts as feed ma­te­rial or even can be up­graded to value added biobased prod­ucts. This kind of EDB is ben­e­fi­cial to op­ti­mize eco­nomic and eco­log­i­cal per­for­mances of the full biomass sup­ply chain. On the other hand, MDB pri­mar­ily gen­er­ates bio based prod­ucts like bio-ma­te­ri­als, lu­bri­cants, chem­i­cals, food, feed etc. and process residues that can be fur­ther pro­cessed or used to pro­duce en­ergy for de­cen­tral­ized ap­pli­ca­tions.

Clas­si­fi­ca­tion of bio-re­finer­ies

Bio-re­finer­ies can be broadly clas­si­fied based on the feed­stock viz: Agri­cul­tural bio-re­fin­ery, ce­real bio-re­fin­ery, oilseed bio-re­fin­ery, green bio-re­fin­ery, lig­no­cel­lu­losic bio-re­fin­ery, forestry bio-re­fin­ery and in­dus­trial or mu­nic­i­pal waste based biore­fin­ery. The avail­abil­ity of the feed­stock for the pro­duc­tion of var­i­ous in­ter­me­di­ates and mar­ketable prod­ucts is a cru­cial fac­tor for the im­ple­men­ta­tion of a biore­fin­ery.

Or­ganic waste biore­fin­ery

In the in­dus­trial or mu­nic­i­pal waste biore­fin­ery, the raw ma­te­rial used is the or­ganic frac­tion of waste pro­duced from in­dus­tries and the waste col­lected at mu­nic­i­pal­i­ties. The mu­nic­i­pal solid waste con­sists of 51% of or­ganic waste that can be uti­lized for the gen­er­a­tion of var­i­ous prod­ucts through a biore­fin­ery ap­proach. The in­put ma­te­rial, process and out­put in­volved in a waste biore­fin­ery is shown in Fig. 2. The most eco-friendly process for de­riv­ing var­i­ous prod­ucts through a bio-re­fin-

ery is through anaer­o­bic diges­tion. Anaer­o­bic diges­tion is a se­quen­tial process con­sist­ing of four stages namely, hy­drol­y­sis, aci­do­ge­n­e­sis, ace­to­ge­n­e­sis and methano­gen­e­sis. At each stage of the anaer­o­bic diges­tion process, mul­ti­ple in­ter­me­di­ates (value added chem­i­cals) and prod­ucts (bio­fu­els, fer­til­izer) can be ob­tained from or­ganic waste as shown in Fig. 2.

Or­ganic waste as a feed­stock for biore­fin­ery

Or­ganic waste streams are a sus­tain­able al­ter­na­tive to fos­sil-based re­sources as they do not com­pete di­rectly with food crops. All the waste streams presently have some value, for in­stance or­ganic frac­tion of MSW, waste gen­er­ated in ho­tels, restau­rants, mar­kets, in­dus­tries etc., is cur­rently be­ing ex­ploited as feed­stock for bioen­ergy (heat and power) pro­duc­tion. It is known that a feed­stock is de­fined as any re­new­able, bi­o­log­i­cal ma­te­rial that can be used di­rectly as a fuel or con­verted to an­other form of fuel or en­ergy prod­uct. These wastes could ef­fec­tively be uti­lized as a feed­stock for biore­fin­ery to ob­tain mul­ti­ple prod­ucts at var­i­ous stages. In ad­di­tion to these, biomass feed­stocks are the plant and al­gal ma­te­ri­als used to de­rive fuels like ethanol, bu­tanol, biodiesel, and other hy­dro­car­bon fuels. Ex­am­ples of biomass feed­stocks in­clude corn starch, sug­ar­cane juice, crop residues such as corn stover and sug­ar­cane bagasse, pur­pose-grown grass crops, and woody plants. As the fos­sil fuel-based re­sources are de­plet­ing day by day, the ex­po­nen­tial in­crease in the va­ri­ety of waste gen­er­a­tion across the globe could be treated as a po­ten­tial re­new­able feed­stock for biore­fin­ery.

Anaer­o­bic diges­tion

Anaer­o­bic diges­tion (AD) is a se­quence of bi­o­log­i­cal pro­cesses for the treat­ment of waste streams to ob­tain value added prod­ucts as de­scribed be­low and shown in Fig. 3 6].

[

Hy­drol­y­sis

The first step of AD is the hy­drol­y­sis of waste ma­te­rial. In this step the hy­drolytic bac­te­ria and the in­her­ent en­zymes present in the waste breaks down the biopoly­mers and other or­ganic ma­te­rial to monomers 7]. For ex­am­ple: Hy­drol­y­sis of lipid mol­e­cules to fatty [ acids, polysac­cha­rides to monosac­cha­rides, pro­teins to amino acids, nu­cleic acids to purines and pyrim­idines etc as shown in Eq.1.

C H O + 2H O C H O + 2H ..... Eq.1[ 1].

6 10 4 2 6 12 6 2

Aci­do­ge­n­e­sis

Aci­do­ge­n­e­sis is the next step of AD in which aci­do­genic mi­cro-or­gan­isms fur­ther break down the hy­drolyzed monomers to prod­ucts such as volatile fatty acids, car­bon diox­ide, hy­dro­gen etc. Aci­do­genic or­gan­isms con­vert the monomer mol­e­cules into or­ganic acids (lac­tic, formic, bu­tyric, acetic acids) ac­etate and car­bon diox­ide, al­co­hols and ke­tones. The prod­ucts formed dur­ing aci­do­ge­n­e­sis are due to a num­ber of dif­fer­ent mi­crobes, e.g., Syn­tro­phobac­ter­wolinii, a pro­pi­onate de­com­poser and Sytrophomonos­wolfei, a bu­tyrate de­com­poser. Other acid for­m­ers are Clostrid­ium spp., Pep­to­coc­cu­saner­obus, Lac­to­bacil­lus, and Acti­no­myces[ 8]. In the acid­i­fi­ca­tion phase, ethanol type fer­men­ta­tion oc­curs, in which the main liq­uid prod­ucts are ethanol and acetic acid. These aci­do­genic bac­te­ria pro­duce an acidic en­vi­ron­ment in the re­ac­tor while cre­at­ing am­mo­nia, H , CO , volatile fatty acids, car­bonic acids, al

2 2 co­hols, as well as trace amounts of other byprod­ucts 9].

[ Ace­to­ge­n­e­sis

In gen­eral, ace­to­ge­n­e­sis is the for­ma­tion of ac­etate, a de­riv­a­tive of acetic acid, from car­bon and en­ergy sources by ace­to­gens[ 10]. These micro­organ­isms ca­tab­o­lize many of the prod­ucts cre­ated dur­ing aci­do­genic phase into acetic acid, CO and H . Ace­to­gens break

2 2 down the or­ganic mat­ter where volatile fatty acids are

pro­duced and trace amounts of ethanol. Aci­do­ge­n­e­sis and ace­to­ge­n­e­sis leads to the for­ma­tion of mix­ture of al­co­hols in­clud­ing volatile fatty acids (acetic acid, bu­tyric acid and pro­pi­onic acid). Methano­gen­e­sis

The last step of AD process is methano­gen­e­sis where the methanogenic bac­te­ria trans­form ac­etate, hy­dro­gen, car­bon diox­ide and for­mate that are end prod­ucts of acid fer­men­ta­tion into meth­ane along with CO and traces of H S,

2 2 N , O . Methanogens be­long to the ar­chae­bac­te­ria,

2 2 which are dif­fer­ent from nor­mal bac­te­ria in cell wall com­po­si­tion, cell mem­branes, coen­zyme, and ri­bo­so­mal RNA se­quences com­po­si­tion. Methanogens are sen­si­tive to oxy­gen and rich in degrad­able or­ganic com­pounds. Some of the ex­am­ples of methanogens in­clude Methanococ­cus, Methanoculleus, Methanofol­lis, Methanopy­rus, Methanosarcina, Methanosphaera, Methan­oth­er­mobac­ter, Methanolacinia­petrolearia, Methanoplanus­lim­i­cola, Methanos­al­sumzhili­nae, Methy­lobac­teri­umphyl­losphaerae, Methanosarcin­abark­eri, Methanosarci­navac­uo­lata 11].

[

Value added prod­ucts­from a biore­fin­ery

Volatile fatty acids

Volatile fatty acids (VFA) are short chain fatty acids con­sistin­gof fewer (2–8) car­bon atoms that can be sep­a­rated through dis­til­la­tion at at­mo­spheric pres­sure. Cur­rently the ex­ist­ing method to pro­duce VFA at com­mer­cial scale is by chem­i­cal route 13]. How­ever,

[

VFA could also be gen­er­ated through bi­o­log­i­cal route us­ing a spe­cially pre­pared mi­cro­bial cul­ture through aci­do­genic AD ap­proach. VFAs has wide va­ri­ety of ap­pli­ca­tions as they are the pre­cur­sors for pro­duc­tion of hy­dro­gen and bio­gas, the can be used in the pro­duc­tion of al­co­hols through hy­dro­gena­tion. In ad­di­tion to these, VFAs can be ex­ploited for bio­plas­tics and bio­fu­els pro­duc­tion 14]. In the re­cent past, gen­er­a­tion of VFA

[ from var­i­ous or­ganic feed­stocks such as food waste 15],

[ press mud[ or­ganic frac­tion of mu­nic­i­pal solid waste

16]

(OFMSW), dairy waste wa­ter etc., was re­ported. A fullscale plant to pro­duce VFA through ther­mal-al­ka­line pre-treat­ment and al­ka­line fer­men­ta­tion of sewage sludge has been built and op­er­ated in China. The av­er­age con­cen­tra­tion of VFA was found to be rang­ing be­tween 3 – 7 g/L with acetic acid be­ing the dom­i­nant prod­uct 17].

[

Bio-hy­dro­gen

Bio-hy­dro­gen pro­duc­tion by con­ver­sion of or­ganic waste through a biore­fin­ery ap­proach is a promis­ing strat­egy to val­orize the waste as well as in­crease the de­mand for im­ple­men­ta­tion of bio-re­finer­ies. Hy­dro­gen is con­sid­ered as one of the clean re­new­able en­ergy car­ri­ers for fu­ture, as the pro­duc­tion of hy­dro­gen can be fea­si­ble in many ways. At present, hy­dro­gen is mostly pro­duced by ther­mo­chem­i­cal pro­cesses such as steam re­form­ing of nat­u­ral gas and coal gasi­fi­ca­tion etc 17]. How­ever, due to the

[ de­ple­tion of fos­sil fuel re­serves as well as en­vi­ron­men­tal con­cerns such as green­house gas emis­sion, ex­plo­ration of other sus­tain­able meth­ods of hy­dro­gen pro­duc­tion is be­com­ing in­evitable. Thus, bi­o­log­i­cal hy­dro­gen pro­duc­tion from or­ganic waste ma­te­rial has gained sig­nif­i­cant im­por­tance[ 18]. A two-stage (aci­do­genic fol­lowed by methanogenic) pi­lot-scale plant was de­signed, man­u­fac­tured and in­stalled at the ex­per­i­men­tal farm of the Univer­sity of Mi­lano for the gen­er­a­tion of hy­dro­gen in first stage and meth­ane in sec­ond stage. This plant is op­er­ated us­ing a biomass mix­ture of live­stock ef­flu­ents mixed with su­gar/starch-rich residues (rot­ten fruits and pota­toes and ex­pired fruit juices), a feed­stock mix­ture based on waste biomasses di­rectly avail­able in the ru­ral area where the plant is in­stalled. A typ­i­cal hy­dro­gen and meth­ane spe­cific pro­duc­tiv­ity of 2.2 and 0.5 Nm3/m3 re­ac­tor per day, in the first and sec­ond stage of the plant re­spec­tively 18].

[

Al­co­hols

The first four al­co­hols in the or­der of car­bon con­tent are methanol, ethanol, propanol, and bu­tanol, are of great­est in­ter­est for fuel use as their chem­i­cal prop­er­ties make them use­ful in in­ter­nal com­bus­tion en­gines 19]. These al­co­hols can be pro­duced through bi­ologi[ cal and chem­i­cal meth­ods. The bi­o­log­i­cal meth­ods of al­co­hol pro­duc­tion in­clude yeast fer­men­ta­tion and aci­do­genic phase of AD. The in­ter­me­di­ates pro­duced dur­ing AD of waste ma­te­rial can be con­verted to al­co­hols through hy­dro­gena­tion process by the ap­pli­ca­tion of re­duc­tion cat­a­lysts. In Brazil and the United States, fuel ethanol is pro­duced by fer­men­ta­tion of corn glu­cose in the US or su­crose in Brazil which are the largest ethanol pro­duc­ers in the world but this can also be

[20] pre­pared from agro-residues ac­cord­ing to the agro-

nomic-based econ­omy of the coun­try. There are some po­ten­tial meth­ods for low cost ethanol pro­duc­tion by us­ing agri­cul­tural wastes 21]. Wheat straw is one of the

[ most abun­dant agri­cul­tural wastes, which has been ex­ten­sively stud­ied 22]. MSW is the low­est cost feed­stock

[ for the gen­er­a­tion of cel­lu­losic bioethanol. It has been re­ported that > 80 bil­lion litres of MSW pa­per de­rived cel­lu­losic bioethanol can be pro­duced world­wide 23].

[

A plant for the gen­er­a­tion of bioethanol from lig­no­cel­lu­losic biomass is be­ing demon­strated at In­dia Gly­cols in Ka­shipur, In­dia 27].

[

Bio-meth­ane

Bio-meth­ane pro­duced by anaer­o­bic diges­tion of or­ganic waste is an al­ter­na­tive gas source to that of the nat­u­ral gas. Bio-meth­ane of­fers enor­mous po­ten­tial as an al­ter­na­tive source of en­ergy, es­pe­cially to fos­sil fuels. Even though its us­abil­ity is known for quite some time, pro­duc­tion of bio-meth­ane started only in the re­cent years be­cause of the ris­ing prices of nat­u­ral gas and high elec­tric­ity prices other fos­sil fuels as well as the threat of global cli­mate change. Chem­i­cally, it is iden­ti­cal to nat­u­ral gas which is stored deep in the ground and is also pro­duced from dead an­i­mal and plant ma­te­rial. How­ever, there are sev­eral im­por­tant dif­fer­ences be­tween bio-meth­ane and fos­sil fuel de­rived meth­ane even though both are pro­duced from or­ganic mat­ter. Meth­ane is about 20 times more po­tent green­house gas than car­bon diox­ide if re­leased into the at­mos­phere[ 24]. Fur­ther­more, its use for power gen­er­a­tion pro­duces heat and emits car­bon diox­ide and some other gases but de­spite that biomethane has sev­eral en­vi­ron­men­tal ben­e­fits which make it a green source of en­ergy. Or­ganic waste ma­te­rial from which bio-meth­ane is pro­duced would re­lease the gas into the at­mos­phere if the waste is sim­ply left to de­com­pose nat­u­rally, while other gases that are pro­duced dur­ing the de­com­po­si­tion process such as ni­trous diox­ide for in­stance fur­ther con­trib­ute to the green­house ef­fect. It was re­ported by Ku­ruti et al., 2017 that a fullscale bio­gas plant based on Anaer­o­bic Gas lift Re­ac­tor Tech­nol­ogy in­stalled at Bel­lary for the treat­ment of 1000 kg/day of food waste (cooked and un­cooked food waste) yielded about 150 m3/day of bio­gas with 65% meth­ane and 200 kg/day of di­ges­tate. Bio­gas could be pu­ri­fied to make Bio-CNG which is equiv­a­lent to CNG (com­pressed nat­u­ral gas). Few plants are work­ing in In­dia to make Bio-CNG from Press mud and agri

[25] cul­ture waste 26].

[

Di­ges­tate

Di­ges­tate is a nu­tri­ent-rich sub­stance pro­duced by AD that can be used as a fer­til­izer.How­ever, the nutri- ents are sig­nif­i­cantly more avail­able in di­ges­tate than in raw slurry i.e. it is eas­ier for plants to make use of the nu­tri­ents present in the di­ges­tate. The residue af­ter the AD of or­ganic waste i.e. di­ges­tate could be ex­ploited as fer­til­izer in liq­uid or solid form de­pend­ing on the re­quire­ment. This helps in the re­duc­tion of us­ing chem­i­cal fer­til­iz­ers. The di­ges­tate that would be ob­tained from AD of dif­fer­ent sub­strates is not sim­i­lar. The Ni­tro­gen, phos­pho­rous and potas­sium con­tent dif­fers. Some typ­i­cal val­ues of nu­tri­ents present in the di­ges­tate are:

• Ni­tro­gen: 2.3 - 4.2 kg/ton

• Phos­pho­rous: 0.2 - 1.5 kg/ton

• Potas­sium: 1.3 - 5.2 kg/ton

Bio-re­fin­ery: An ap­proach to im­prove bio-based econ­omy

Bio-re­finer­ies en­able the ef­fec­tive reuse of waste ma­te­ri­als as re­new­able feed­stock for ma­te­ri­als and en­ergy re­cov­ery. Re­source-ef­fi­cient use of bio-based re­sources also re­duces waste and pol­lu­tion. Broad range of end prod­ucts can be pro­duced from biore­finer­ies and they can cre­ate pro­duc­tion sys­tems that dra­mat­i­cally re­duce the in­put needed as well as waste and sup­port new bio-based in­dus­tries and the ‘green­ing’ of tra­di­tional in­dus­tries. A bio-based econ­omy has the po­ten­tial to con­trib­ute sig­nif­i­cantly to the re­duc­tion in CO emis­sions as well as meet the en­ergy and

2 eco­nomic goals. For ex­am­ple, the sep­a­rate col­lec­tion of bio-waste and its treat­ment through anaer­o­bic diges­tion in a bio-re­fin­ery serves as ap­plied cli­mate pro­tec­tion as there is a con­comi­tant pro­duc­tion of val­ueadded chem­i­cals, bioen­ergy and a so­lu­tion to waste dis­posal is­sue. Shift­ing to­wards a bio-based econ­omy cre­ates new busi­ness op­por­tu­ni­ties in the agri­cul­tural, forestry and in­dus­trial sec­tors etc. By sup­port­ing new bio-based in­dus­tries and the ‘green­ing’ of tra­di­tional in­dus­tries, a bio-based econ­omy will change. A so­cially and en­vi­ron­men­tally ben­e­fi­cial bio-based econ­omy al­ready ex­ists to some ex­tent, but their ef­forts need to be put to im­ple­ment and flour­ish the bio-re­finer­ies to avail mul­ti­ple ben­e­fits.

Con­clu­sion

A suc­cess­ful biore­fin­ery will ful­fill two strate­gic goals i.e. re­plac­ing non-re­new­able raw ma­te­ri­als such as fos­sil fuels with re­new­able or­ganic ma­te­rial such as biomass, or­ganic waste etc., and pro­vides eco­nomic in­cen­tive to sup­port a ro­bust bio-re­fin­ing in­dus­try (an eco­nomic goal, met by the pro­duc­tion of high value chem­i­cals). Meet­ing the en­ergy cri­sis by the gen­er­a­tion

of bio­fu­els and reach­ing the set eco­nomic goal would be met by the pro­duc­tion of the high value-added chem­i­cals through the im­ple­men­ta­tion of bio-re­finer­ies.

Ac­knowl­edge­ment

The au­thors are thank­ful to the Gov­ern­ment of In­dia; Coun­cil for Sci­en­tific and In­dus­trial re­search (CSIR), for fund­ing the projects. The au­thors are also grate­ful to the Di­rec­tor-In­dian In­sti­tute of Chem­i­cal Tech­nol­ogy (IICT) for his en­cour­age­ment in car­ry­ing out this work.

Ref­er­ences

1. Hughes, S., Moser, B. and Gib­bons, W. (2014). Mov­ing To­ward En­ergy Se­cu­rity and Sus­tain­abil­ity in 2050 by Re­con­fig­ur­ing Bio­fuel Pro­duc­tion. Con­ver­gence of Food Se­cu­rity, En­ergy Se­cu­rity and Sus­tain­able Agri­cul­ture, pp.15-29.

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28. http://www.dbtin­dia.nic.in/in­dia’s-first-cel­lu­losic-al­co­holtech­nol­ogy-demon­stra­tion-plant-to-be-in­au­gu­rated-in-ka­shipur-ut­trak­hand/

Fig.2 Or­ganic waste biore­fin­ery [5]

Fig. 1 Pe­tro­leum re­fin­ery v/s Biore­fin­ery

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