9 research outputs found
Integrated bioenergy and animal feed production from AFEX TM and steam exploded sugarcane residues
Thesis (PhD)--Stellenbosch University, 2019.ENGLISH ABSTRACT: Current and future trends demonstrate that the increasing world population, dwindling arable
land, changing human diets and increased demand for (bio)energy present an opportunity to redesign
the way land is used to meet the future food, feed and bioenergy demands. The sustainable
integration of bioenergy and highly digestible livestock feed production systems has been touted as a
potential avenue to increase the economic returns to agriculture and simultaneously promote energy
security, particularly in developing countries. To this end, post-harvest residues from sugarcane
processing (i.e. sugarcane bagasse (SCB) and cane leaf matter (CLM)) have emerged as candidate
feedstock for integrated bioenergy (e.g. bio-ethanol and biogas) and animal feeds production in South
Africa and Brazil. The principal aim of this dissertation was to perform a systematic comparison of the
potential use of steam explosion (StEx) and ammonia fiber expansion (AFEXTM) as pretreatment
technologies to overcome biomass recalcitrance, thereby generating highly digestible animal feeds,
and cellulosic ethanol and biogas production feedstocks from sugarcane residues for future integrated
biofuel-animal feed systems.
A side-by-side comparison of the effect of StEx and AFEXTM pretreatment of sugarcane
residues revealed AFEXTM to be the better pretreatment for maximising ethanol yields per Mg raw dry
material (RDM) from both SCB and CLM. Under industrially relevant solids loadings of 16% and
dosages of 9.8 mg protein/g RDM, AFEXTM pretreated sugarcane residues generated ethanol yields up
to 324 litres/Mg RDM, the highest ethanol yields reported in literature from sugarcane residues. In
contrast, ethanol yields from steam exploded sugarcane residues were limited to the range 205 to 257
litres/Mg RDM primarily due to the compounded effect of carbohydrate degradation during
pretreatment, enzyme inhibition and microbial inhibition of recomninant Saccharomyces cerevisiae
424A (LNH-ST) during fermentation.
To debottleneck microbial inhibition during the fermentation of non-detoxified StEx whole
slurry’s, the potential use of industrial xylose-fermenting S. cerevisiae strains as efficient and inhibitor
tolerant ethanologens was evaluated. S. cerevisiae strains CelluXTM 4 and TP-1 demonstrated near
complete glucose and xylose consumption, with high acetate resistance, furan detoxification and
phenolic aldehyde detoxification phenotypes. Ultimately, both strains facilitated the generation of
224 litres/Mg RDM from non-detoxified StEx SCB whole slurry under a pre-hydrolysis simultaneous
saccharification and co-fermentation (PSSCF) configuration. In comparison, the same yeast strains
generated moderately higher ethanol yields (254 litres/Mg RDM) during the PSSCF of highly
fermentable AFEXTM-treated SCB, demonstrating that the difference in the potential ethanol yields that
can be recovered from the two pretreatment technologies can be significantly reduced by using
inhibitor-tolerant ethanologens.
With both AFEXTM and StEx-treated sugarcane residues requiring enzyme dosages of 9.8mg
protein/g RDM to achieve high ethanol yields, the potential use a room-temperature Cellulose IIIIactivation (CIIII-activation) process to enhance the digestibility of StEx- or AFEXTM-treated sugarcane
residue pellets was investigated as a potential strategy to minimise the enzyme cost contribution per
unit volume ethanol produced. Coupling AFEXTM sugarcane lignocelluloses with CIIII-activation
reduced of the enzyme dosage requirements by more than 60% (to ~3 mg protein/g RDM), whilst
achieving ethanol yields greater than 280 litres/Mg RDM. These results represented the lowest
enzyme dosage to achieve ethanol yields of 280 L/Mg RDM reported in literature. In contrast,
upgrading StEx-treated sugarcane residue pellets could only facilitate ethanol yields up to 201
litres/Mg RDM at an enzyme dosage of ~3 mg protein/g RDM.
Besides ethanol production, both AFEXTM and StEx also demonstrated significant
improvements in the animal feed value of SCB and CLM. AFEXTM-treated sugarcane residues were
characterized by 230% increase in the non-protein nitrogen content of the biomass, and up to 69%
and 26% improvement in the in-vitro true digestibility (IVTD) and metabolizable energy (ME),
respectively, relative to untreated controls (P < 0.05). Although StEx did not increase the nitrogen content of the pretreated sugarcane residues, the IVTD and ME of StEx-treated SCB and CLM were
improved by 54% and 7%, respectively (P < 0.05). These results demonstrated that both AFEX and StEx
pretreatment can simultaneously generate highly digestible animal feeds and enhanced cellulosic
ethanol feedstocks from sugarcane residues.
The combination of the near optimal C/N ratios and structural modifications of AFEXTM-treated
sugarcane residues also facilitated biogas production with methane yields up to 299 L CH4/kg VS, with
or without co-digestion with dairy cow manure (DCM). To obtain comparable methane yields,
untreated and steam exploded (StEx) sugarcane residues had to be co-digested with DCM, at mass
ratios providing initial C/N ratios in the range of 18 to 35. Furthermore, the solid digestates recovered
from the co-digestion of the sugarcane lignocelluloses with DCM were enriched in nitrogenphosphate-potassium (NPK), suggesting that they could be used as biofertilizers or partial
replacements for the CLM that is typically left on the field during green cane harvesting.
The results from this dissertation showed that both AFEXTM and StEx successfully enhanced the
ethanol production potential, methane production potential, and animal feed value of sugarcane
residues, providing alternative models for the sugarcane industry to create bioenergy and food value
from sugarcane residues. Ultimately, these results provide essential information and insights for
future techno-economic and life-cycle analyses that are required to establish the preferred
pretreatment technology and processing strategies to enable economically viable and
environmentally sustainable integrated bioenergy and animal feed production from South African
sugarcane residues.AFRIKAANSE OPSOMMING: Huidige en toekomstige tendense dui daarop dat die toename in die wêreldbevolking,
drastiese afname in bewerkbare grond, verandering in menslike diëte en verhoging in die vraag na
(bio-)energie ’n geleentheid bied vir die herontwerp van grondgebruik om in toekomstige voedsel-,
voer- en bio-energiebehoeftes te voorsien. Die volhoubare integrasie van produksiestelsels vir bioenergie en hoogs verteerbare veevoer word as ’n moontlikheid beskou om die ekonomiese opbrengs
van landbou te verhoog en terselfdertyd energiesekerheid te bevorder, veral in ontwikkelende lande.
Die naoesreste van suikerrietverwerking (d.w.s. suikerrietbagasse (SRB) en rietblaarmateriaal (RBM))
word as kandidaatvoerstof vir geïntegreerde bio-energie- (bv. bio-etanol- en biogas-) en
veevoerproduksie in Suid-Afrika en Brasilië beskou. Die hoofdoel van hierdie verhandeling was om ’n
stelselmatige vergelyking te onderneem van die moontlike gebruik van stoomontploffing (“StEx”) en
ammoniakveseluitsetting (AFEXTM) as voorbehandelingstegnologieë om enersyds die
biomassaweerspannigheid van suikerrietreste te bowe te kom en sodoende hoogs verteerbare
veevoer te skep, en andersyds sellulosiese etanol- en biogasproduksievoerstof uit suikerrietreste te vervaardig vir toekomstige geïntegreerde biobrandstof-veevoerstelsels.
Wanneer die uitwerking van StEx- en AFEXTM-voorbehandeling van suikerrietreste naas
mekaar beskou word, blyk AFEXTM die beter voorbehandeling te wees vir maksimum etanolproduksie
per Mg onverwerkte droëmateriaal (ODM) vir sowel SRB as RBM. Met industrieel relevante
vastestofladings van 17% en ’n dosis van 9,8 mg proteïen/g ODM, bied AFEXTM-voorbehandelde
suikerrietreste ’n etanollewering van tot 324 liter/Mg ODM, synde die hoogste etanollewering uit
suikerrietreste wat tot nog toe in die literatuur aangemeld is. Daarteenoor is die etanollewering van
stoomontplofte suikerrietreste beperk tot tussen 205 en 257 liter/Mg ODM, hoofsaaklik weens die saamgestelde uitwerking van koolstofafbreking gedurende voorbehandeling, ensieminhibisie en
mikrobiese inhibisie van Saccharomyces cerevisiae 424A (LNH-ST) gedurende fermentasie.
Om die bottelnek van mikrobiese inhibisie gedurende die fermentasie van niegedetoksifiseerde StEX-ru-flodder uit die weg te probeer ruim, is die potensiële gebruik van industriële
xilose-fermenterende S. cerevisiae-stamme ook ondersoek. Die S. cerevisiae-stamme CelluXTM 4 en TP1 het byna volledige glukose- en xiloseverbruik, hoë asetaatweerstandigheid, furaandetoksifikasie- én
fenoliese-aldehied-detoksifikasiefenotipes getoon, en het uiteindelik ’n etanollewering van
224 liter/Mg ODM gebied in ’n konfigurasie van pre-hidrolise- gelyktydige versuikering en
gesamentlike fermentasie (“PSSCF”). Daarteenoor het die PSSCF van hoogs fermenteerbare AFEXTMbehandelde SRB ’n effens hoër etanollewering getoon (254 liter/Mg ODM), wat daarop dui dat die
verskil in die moontlike etanollewering van die twee voorbehandelingstegnologieë beduidend
verminder kan word met behulp van inhibitorverdraagsame etanologene.
Daarbenewens is daar ondersoek ingestel na die opgradering van verpilde StEx- of AFEXTMbehandelde suikerrietreste deur middel van ’n CIIII-aktiveringsproses (CIIII) by kamertemperatuur om
die bottelnek van die hoë ensiemdosisvereistes verbonde aan hoë etanollewering te probeer
verwyder. Die kombinasie van AFEXTM-suikerrietlignosellulose en CIIII het die ensiemdosisvereistes
met meer as 60% verlaag (tot ~3 mg proteïen/g ODM) en etanollewering tot meer as
280 liter/Mg ODM verhoog. Hierdie resultaat is die laagste ensiemdosis vir ’n etanollewering van
280 L/Mg ODM wat tot dusver in die literatuur aangemeld is. Daarteenoor het die opgradering van
verpilde StEx-behandelde suikerrietreste ’n etanollewering van slegs 201 liter/Mg ODM by ’n
ensiemdosis van ~3 mg proteïen/g ODM teweeggebring.
Benewens die uitwerking op etanolproduksie, blyk sowel AFEXTM as StEx ook aansienlike
verbeteringe in die veevoerwaarde van SRB en RBM tot gevolg te hê. Die biomassa van AFEXTMbehandelde suikerrietreste het tipies oor ’n 230% hoër nieproteïenstikstofinhoud beskik, en in vitroware verteerbaarheid (IVWV) en metaboliseerbare energie (ME) was onderskeidelik 69% en 26% hoër
as by onbehandelde kontroles (P < 0,05). Hoewel StEx nie die stikstofinhoud van die voorbehandelde suikerrietreste verhoog het nie, het die IVWV en ME van StEx-behandelde SRB en RBM met
onderskeidelik 54% en 7% verhoog (P < 0,05). Hierdie resultate toon dat sowel AFEX- as StExvoorbehandeling terselfdertyd hoogs verteerbare veevoer én beter sellulosiese etanolvoerstof uit
suikerrietreste kan oplewer.
Die kombinasie van die byna optimale C/N-verhoudings en strukturele aanpassings van AFEXTMbehandelde suikerrietreste het ook biogasproduksie teweeggebring, met ’n metaanlewering van tot
299 L CH4/kg VS, met óf sonder gesamentlike vertering met melkbeesmis (MBM). Om vergelykbare
metaanlewering te verkry, moes onbehandelde en stoomontplofte (StEx-) suikerrietreste saam met
MBM verteer word, wat op massaskaal aanvanklike C/N-verhoudings van tussen 18 en 35 gelewer het.
Daarbenewens was die vaste digestate wat uit die gesamentlike vertering van die
suikerrietlignosellulose en MBM herwin is, ryk in stikstof-fosfaat-kalium (NPK), wat daarop dui dat dit
as biobemesting of gedeeltelike plaasvervanger kan dien vir die RBM wat gewoonlik gedurende groen
oesting op landerye agterbly.
Die resultate van hierdie studie toon dat sowel AFEXTM as StEx die etanolproduksiepotensiaal,
metaanproduksiepotensiaal en veevoerwaarde van suikerrietreste suksesvol verhoog, en sodoende
die suikerrietbedryf van alternatiewe modelle voorsien om bio-energie en voedselwaarde te skep. Die
bevindinge bied noodsaaklike inligting en insigte vir toekomstige tegno-ekonomiese en
lewensiklusontledings om te bepaal watter voorbehandelingstegnologie en verwerkingstrategieë die
beste sal werk om geïntegreerde bio-energie- en veevoerproduksie uit Suid-Afrikaanse suikerrietreste
ekonomies lewensvatbaar en omgewingsvolhoubaar te maak.Doctora
The development and modeling of an ethanol production biocatalytic system with cell retention
Thesis (MEng) -- Stellenbosch University, 2014.ENGLISH ABSTRACT: See PDF for abstract.AFRIKKANSE OPSOMMING: Sien PDF vir die opsomming
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MOESM2 of Ethanol production potential from AFEX™ and steam-exploded sugarcane residues for sugarcane biorefineries
Additional file 2: Table S2. AFEX™ -bagasse pretreatment conditions used for evaluating the effect of pretreatment conditions on the monomeric glucose, xylose and combined sugar yield using a central composite design of experiments (DOE)
MOESM6 of Ethanol production potential from AFEX™ and steam-exploded sugarcane residues for sugarcane biorefineries
Additional file 6: Fig. S4. Material balances during pretreatment, washing, hydrolysis and fermentation for Processes I–IV
MOESM5 of Ethanol production potential from AFEX™ and steam-exploded sugarcane residues for sugarcane biorefineries
Additional file 5: Fig. S3. Statistical optimization of Cellic® CTec3, Cellic® HTec3, Pectinex Ultra-SP combinations for maximizing combined glucose and xylose yields from AFEXTM and Steam exploded sugarcane bagasse and CLM
MOESM4 of Ethanol production potential from AFEX™ and steam-exploded sugarcane residues for sugarcane biorefineries
Additional file 4: Fig. S2. Profiling the effect of ammonia loading and temperature on the combined glucose and xylose yields for AFEX™-treated bagasse and cane leaf matter after 1% glucan loading enzymatic hydrolysis with 15 mg protein g−1 glucan
Development of an ammonia pretreatment that creates synergies between biorefineries and advanced biomass logistics models
ABSTRACT: A novel ammonia-based pretreatment for densified lignocellulosic biomass was developed to reduce ammonia usage and integrate with viable biomass logistics scenarios. The COmpacted Biomass with Recycled Ammonia (COBRA) pretreatment performed at 100 degrees C allows >95% conversion of sugarcane bagasse (SCB) carbohydrates into soluble monomeric and oligomeric sugars (glucose and xylose) using industrially relevant 6% glucan loading (similar to 21% solids loading) enzymatic hydrolysis conditions at reduced enzyme loadings. Pretreatment via COBRA with simultaneous lignin extraction (COBRA-LE) improved Saccharomyces cerevisiae 424A(LNH-ST) metabolic yield from 89% to 97.5% relative to COBRA without delignification, allowing a process ethanol yield of 71.6%. A technoeconomic analysis on SCB biorefining to ethanol in the state of Sao Paulo, Brazil, compared COBRA to other mature technologies, such as AFEX and steam-explosion. Amongst all scenarios studied, biorefineries based on COBRA-LE pretreatment offered the lowest average minimum ethanol selling price of US$1.45 per gallon ethanol. COBRA pretreatment was subsequently tested on perennial grasses and hardwoods, and >80% total sugar yields were achieved for all cases.info:eu-repo/semantics/publishedVersio