Location: Sustainable Biofuels and Co-products Research
Project Number: 8072-41000-112-007-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Sep 4, 2024
End Date: Nov 30, 2027
Objective:
Pyrolysis is a maturing technology for thermochemical conversion of abundant agricultural biomass to value added products such as fuels and chemicals. One issue that impedes the large-scale development of biomass pyrolysis is that the pyrolytic liquid is composed of two phases: an organic-rich phase (bio-oil) and a water-rich phase (aqueous phase), exhibiting multiphase behavior and complicating the downstream upgrading processes. The organic bio-oil can be upgraded to high-value chemical products, including intermediates that can be used in existing refineries to replace fossil oil, and end products such as sustainable aviation fuels. However, the aqueous phase contains low concentrations of water-soluble organics (~5 wt% C in water, depending on the feedstock), which are energy intensive to recover via extraction or reforming and the low recovery yields may not justify the cost. An alternative to recovering the organics is to treat the aqueous phase as a waste or as recycle water for irrigation; however, pretreatment is required to reduce the total organic carbon (TOC) below government-regulated levels or to eliminate organics that make it unsuitable for direct irrigation application.
The objective of the proposed work is to develop a low-carbon intensity thermochemical conversion technology for olive mill solid residue, an abundant agricultural waste in Israel, to value-added products. Since it is energy intensive to recover products from the aqueous phase bio-oil, cost-effective water pretreatment methods will be developed to make it suitable for municipal waste disposal or as recycled water for irrigation. By the end of the project, the proposed approach (pyrolysis + aqueous phase pretreatment) will be compared to the alternate approaches of pyrolytic aqueous phase reforming based on a preliminary technoeconomic analysis.
Approach:
Fast pyrolysis coupled with pretreatment of the pyrolytic aqueous phase will be developed for olive mill solid waste (OMSW), an abundant agricultural waste biomass in Israel. The reaction conditions for OMSW fast pyrolysis will be optimized by ARS investigators to maximize bio-oil yield and quality. Both microwave and conventional pyrolysis will be tested for comparison. The composition of the pyrolysis products (organic bio-oil, aqueous bio-oil, biochar, and noncondensible gas) will be analyzed by ARS investigators to compare the carbon efficiency and energy efficiency of each method for conversion of OMSW to valuable products. The chemical composition of the aqueous phase bio-oil will be used to synthesize a model aqueous phase solution by cooperators at Tel Aviv University using commercial chemicals for pretreatment testing. Two pretreatment methods will be developed for organic removal from the synthesized aqueous phase solution using (1) submerged plasma arc pretreatment and (2) ozonation by researchers at Tel Aviv University. The toxicity analysis of the model aqueous phase bio-oil samples before and after pretreatment will be carried out by collaborators at Oranim College to ensure organic removal below target concentrations. The optimized pretreatment conditions using the two pretreatment methods will be validated on real pyrolytic aqueous phase samples and the toxicity reduction will be evaluated. An economic analysis of the OMSW pyrolysis with aqueous phase pretreatment will be used to compare the two pretreatment methods and evaluate the economic competitiveness of this approach with alternate approaches for small scale pyrolysis and water treatment. Further, a preliminary engineering design of the pyrolysis and pretreatment processes at meaningful scale will be drafted.
