Recipient Organization
UNIV OF IDAHO
875 PERIMETER DRIVE
MOSCOW,ID 83844-9803
Performing Department
Biological Engineering
Non Technical Summary
Agriculture is the fabric of rural America, economically and socially; however, modern agriculture is facing waste management issues that, if not remedied, will harm this industry and the associated communities. Historically, most agricultural waste has simply been viewed as a byproduct to be disposed of; often little-to-no value is recovered (other than limited energy production and re-purposing as animal feed). However, perceptions have changed; as defined by Congress (U.S. Code Title 7, Section 31030), sustainable agriculture is an integrated system of plant/animal production practices that have a site-specific application to: (1) satisfy human food needs; (2) enhance the environmental quality and natural resource base upon which the agricultural economy depends; (3) make the most efficient use of nonrenewable and on-farm resources and integrate natural biological cycles and controls; (4) sustain the economic viability of farm operations; and (5) enhance the quality of life for farmers and society as a whole.One specific agricultural waste of concern is dairy manure. Over 30% of the nation's dairy cows and 3 of the top 10 dairy states (CA #1, ID #3, WA #10) are located in the region. The economic value of the industry to the region is extraordinary. For example, based on data from the United Dairymen of Idaho, in 2011 on-farm cash receipts from milk produced at Idaho dairies amounted to $2.45 billion dollars ranking it as the largest single sector in the state's agriculture industry. Idaho dairies and allied industries employ >36,000 people. However, U.S. dairy economic stability is challenged due to increased attention on waste management and associated environmental impacts. Over 9 million dairy cows generate >226 billion kg (249 million tons) of wet manure and ~5.8 billion kg of carbon dioxide (CO2) equivalents annually in the U.S.These emissions constitute ~7% of the 2005 greenhouse gasses in the U.S. and make dairies one of the largest single industry sources. Further, each ton of manure contains 4.5 kg of N and 0.8 kg of P; improper manure disposal can impair ground and surface waters. Lagoon systems are used most commonly to manage manure, however, lagoons do little to recover value from this resource or achieve treatment. More recently anaerobic digestion (AD) has been advocated, with the coupled goal of producing electricity from CH4-rich biogas. However, conventional manure AD technology is not sufficiently economical, reliable, or stable to support widespread use at dairies. Beyond implementation realities, AD does not recover all the high value organic matter; in fact, no current manure management practice captures the real value of this resource.Despite the above challenges faced in managing dairy manure, real economic potential nonetheless exists in this waste stream. The proposed research will advance a sustainable processfor the conversion of targeted byproduct streams to bioplastics (polyhydroxybutyrate-co-hydroxyvalerate (PHBV)) that exhibit tunable properties for multiple applications. In our process, organic-rich wastes are fermented to produce volatile fatty acids (VFAs), which are aerobically converted by a mixed microbial consortium (MMC) to form random and block-copolymer PHBV.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
Objective 1 - Establish operating parameters to synthesize random and co-block PHBV polymers using blends of fermented organic-rich feedstocks. As illustrated (Fig. 1), our PHBV technology involves (1) fermentation to produce VFAs; (2) sustaining a microbial catalyst capable of hyper PHBV synthesis (in the "enrichment" reactor); and (3) PHBV production using the catalyst. With fermented dairy manure as a model substrate, we have refined our understanding of feast-famine PHBV metabolisms such that we can manipulate operations to maintain a catalyst capable of hyper-producing PHBV. Moreover, we have (1) a mobile pilot-scale PHBV system and (2) a 20-L extraction unit for obtaining large quantities of PHBV for materials evaluation. Collectively these capabilities position us to evaluate PHBV production from other waste streams at a pre-commercial scale. This research will focus on PHBV production on a fermented dairy manure (with investigations augmented using sugar beet wastewater).We hypothesize that PHBV synthesis can be controlled through form of substrate (i.e., specific blends of VFAs) to produce polymers with unique structure, material properties, and processing characteristics. This hypothesis is based on observations that mixed microbial consortia cultured on specific VFAs (pure vs. mixed) synthesize unique forms of PHBV. In particular, mixed VFAs generate a random PHBV block; pure acetate or lactate generate a PHB block; and pure propionate yields a PHV block. Under this objective, investigations will be conducted to establish PHBV production reactor operating criteria to generate specific copolymer forms with unique engineered material properties; results will create opportunities to tailor the technology for diverse applications.Objective 2 - Determine the PHBV polymer structure-property relationships. Coupled with Obj. 1 investigations, during PHBV production we will characterize substrate effects on the synthesized PHBV.
Project Methods
Objective 1 - Establish operating parameters to synthesize random and co-block PHBV polymers using blends of fermented organic-rich feedstocks. A 20-L PHBV enrichment reactor will be operated (consistent with prior investigations [23, 41, 43]) to provide catalyst. The enrichment reactor will be sustained on fermented dairy manure, produced consistent with previous investigations [23, 43, 53, 54]; fermenter liquor VFA concentrations will be regularly monitored by GC/FID [53]. PHBV content will be determined as methyl ester derivatives by GC/MS [53, 55].Investigations will focus on three VFA substrates (initially as synthetic VFAs; ultimately VFAs from Task 1.1): (1) mixed VFAs (generates a PHBV block), (2) pure acetate or lactate (PHB block), and (3) pure propionate (PHV block). With three substrates added in different combinations for an assumed six pulse-feed intervals, a minimum of 28 PHBV Production reactor combinations will be evaluated in triplicate (a total of 84 tests). Replicate analyses will establish potential bioprocess variability associated with the PHBV catalyst obtained from the enrichment reactor. While there is potential for catalyst population dynamics to vary over time, research has observed negligible effects from a similar substrate [56]. Moreover, our research has shown that the enrichment catalyst exhibits a consistent metabolic potential and state with seemingly diverse capabilities to produce varying forms of PHA [42]. Each production reactor scenario will be inoculated with the enrichment reactor microbial catalyst obtained at peak intracellular PHBV concentration (i.e., recovered at approximately 1 to 2 hours into a cycle [23, 40, 41, 43]). Substrate will be added in time increments/volumes to maintain an extended PHBV 'feast' response (e.g., Fig. 4). We have established methods to determine when VFAs should be added to maximize and sustain a feast condition [23, 36, 41, 57, 58]; the method also indicates intracellular PHBV saturation.Objective 2 - Determine the PHBV polymer structure-property relationships. Microbes will be lysed to cease metabolic activity and maintain PHBV concentrations [59], then centrifuged and lyophilized. PHBV will be extracted with chloroform and purified [59], then chemically characterized and quantified by GC/MS [23, 37, 40, 44, 53, 55]. PHBV Mw will be determined by gel permeation chromatography [60]. FTIR spectroscopy will be performed to determine the degree of PHBV crystallinity and purity check during PHBV isolation and purification. Sequence information will be determined from diad and triad HV/HB sequence information from the 13C NMR spectra [24]. PHBV monomer sequence will be determined on partially hydrolyzed PHBV by ESI-MS [24]. Data sets will be statistically analyzed to confirm relationships between the substrate regime and PHBV yield, HB/HV distribution, and material characteristics. Multivariate analysis will be applied to mine the data to discover potentially critical relationships.