1a. Objectives (from AD-416):
Develop catalytic and non-catalytic technologies that enable commercially-viable processes for on-farm scale production of stable and transportable pyrolysis oils that meet boiler fuel or refinable crude oil specifications. Sub-Objective 1: Quantify the effect of various agricultural feedstocks (varying in composition, maturation, post-harvest handling, and pre-treatment) on the pyrolysis process efficiency, kinetics, product yield (pyrolysis oil, syngas, and charcoal), and composition. Sub-Objective 2: Develop commercially preferred catalytic and non-catalytic processes for on-farm scale production of stable and transportable pyrolysis oils that meet specifications as boiler fuel or refinable crude oils. Sub-Objective 3: Develop technologies that enable commercially-viable fast pyrolysis and post-pyrolysis processes for biochar production from a variety of agricultural feedstocks.
1b. Approach (from AD-416):
A stepwise approach will be taken to address the objective by carrying out a series of experiments organized under the three sub-objectives. The first approach will involve screening of biofeedstocks using existing laboratory (desk-top) pyrolysis units to determine their potential use as second generation biomass feedstock. Under this same sub-objective, catalysts with the potential to stabilize pyrolysis liquid, when added to the biomass, will be screened. Under the second sub-objective large scale experiments will be carried out in the ARS fluidized-bed pyrolysis reactor with selected biomass and selected catalysts. Additional experiments will be designed under this sub-objective to explore non-catalytic pathways for producing stabilized pyrolysis oil. The next set of experiments, to be organized under sub-objective 3, will be designed to develop post-pyrolysis processes that will generate biochar with soil-amending, carbon sequestering properties. Modifications, incorporating changes that the experimental outcomes and analyses results will dictate, will be made to the pilot reactor system so as to make it compatible with the distributed scale systems envisioned for the on-farm approach.
3. Progress Report:
(i) Sub-obj-1: (1) We continued to characterize switchgrass for its response to catalytic and non-catalytic pyrolysis. Variables studied for switchgrass included genotype and stage of maturity when harvested. This work was done in collaboration with CenUSA. (2) We studied the fast pyrolysis of horse manure for local utilization of the bio-oil produced. Using data from fast pyrolysis at ERRC, a technoeconomic model was developed for the potential to locally produce and utilize bio-oil. In a case study based on an equine rehabilitation facility where bio-oil produced from horse waste replaces diesel fuel used for heating the facility found that it could be economical at 5 tons per day. (3) We continued our work looking at the effect of utilizing proteinacous biomass compared with mostly lignocellulosic biomass. Previously we found that fast pyrolysis of proteinacous biomass, produced bio-oil with higher energy content and lower oxygen content compared with that from wood/grasses. We have further demonstrated that after undergoing mild hydrotreatment the bio-oil from oil seed presscakes has less heteroatom content and contains more petroleum-like long hydrocarbon chains than bio-oil from wood undergoing the same treatment. (4) We have studied the mild pyrolysis of switchgrass/polyhydroxybutyrate (PHB) blends as a model for switchgrass genetically modified to produce PHB. We can produce the valuable chemical crotonic acid from decomposition of PHB along with bio-oil and bio-char from switchgrass. This work is done in collaboration with Metabolix (CRADA). (5) We have fractionated bio-oil to separate various fractions of pyrolyzed lignin fragments from bio-oil. These materials are potential feedstocks for production of substituted aromatics as fine chemicals. Testing of these isolated materials for reaction with C-O bond breaking homogenous catalysts for production of chemicals is underway. (ii) Sub-obj-2: (1) Non-catalytic pyrolysis: Design of a two ton per day dual fluidized bed pyrolysis called, Combustion Reduction Integrated Pyrolysis System (CRIPS) for demonstration on-farm pyrolysis is complete and construction is underway. (2) Catalytic Pyrolysis: Studies on in situ catalytic pyrolysis, where pyrolysis and catalysis occur in the same fluidized bed reactor are complete for studies on oak wood utilizing zeolite catalysts from UOP as part of DOE py-oil stabilization program (CRADA). Further studies are underway at studying short and long term zeolite catalyst deactivation for similar processes using switchgrass. (3) Catalytic Pyrolysis: We have scaled up our ex situ vapor cracking studies by building a secondary fixed bed reactor for secondary catalytic processing of full stream pyrolysis vapors on the pilot scale. (iii) Sub-obj-3: We have performed steam activation of fast pyrolysis bio-char from several feedstocks to further develop the surface areas and porosity required for several applications. We have compared the usefulness of these chars for removing heavy metals and organic containments from water. Studies are under-way comparing bio-char utilization in soil for plant growth.
1. Development of 13C NMR based Chemometric model for bio-oil characterization and classification. Bio-oils produced from various biomass sources are very complex chemical mixtures which can differ, sometimes greatly based the material processed. Characterization of bio-oils is a challenging task usually requiring utilization of several different techniques many of which can only analyze a portion of the material. We used a technique called 13C nuclear magnetic resonance (NMR) which can provide information on the types of chemical components in the bio-oil, and it can look at the entire bio-oil rather than just a portion. We performed this analysis on bio-oils produced from several feestocks including woods, energy crops, crop residues, oil seed residues and animal wastes. Utilizing NMR and statistical methods ARS researchers at Wyndmoor, Pennsylvania were able to develop a method to classify bio-oils quickly using only one analysis.
2. Production of deoxygenated bio-oil via catalytic pyrolysis. The largest source of feedstock to produce advanced biofuels is lignocellulosic biomass, including woody materials, herbaceous grasses and crop residues (e.g. corn stover, straws). One promising process to convert biomass to a liquid is pyrolysis which produces a product called bio-oil which can be refined to “green” gasoline and diesel fuels. However, bio-oil is currently incompatible with petroleum for refining because it is corrosive and unstable because it consists largely of reactive oxygen-containing molecules. One method to reduce the oxygen content of pyrolysis oil is to incorporate a catalyst material that acts to facilitate the removal of oxygen from the molecules that make up bio- oil resulting in hydrocarbons, the types of compounds found in petroleum. Using this method, ARS researchers at Wyndmoor, Pennsylvania were able to reduce the oxygen content in bio-oil from about 40 wt% to about 17 wt%.
Boateng, A.A., Mtui, P.L. 2012. CFD modeling of space-time evolution of fast pyrolysis products in a bench-scale fluidized-bed reactor. Applied Thermal Engineering. 33-34:p.190-198.