Biomass

BIOMASS CHARACTERIZATION; CHEMICAL


CHNS, Bomb Calorimeter. Click for larger version of photo >>


Ankom Fat Extractor


SEM of pyrolyzed poultry litter char

Biorefineries are integrated processing factories that use biomass to produce multiple products such as fuels and chemicals. In order for a Biorefinery to reach its maximum potential, it has to have the capability of using multiple types of input biomass. This poses a fundamental problem because different biomasses have different physical and chemical properties, and these impact their effectiveness in individual downstream processes. In current approaches, a downstream process is optimized for a specific biomass input by matching processing conditions to biomass properties. The goal of this focus area in our program is to measure and document properties of various types of biomass (with focus on those found in Georgia and the Southeastern United States) how these properties impact downstream processes, and how they can be modified. This program focus area interfaces closely with all downstream processing areas, and to preprocessing options to enhance properties of biomass.

Table 1. Characterization of pine and peanut hull pellet biomass
Parameter Feedstock
Pine Peanut hull
Moisture, w.b. 7.4 8.6
Volatiles, d.b. 80.9 71.7
Ash, d.b. 0.1 4.2
Lignin (wt %) 26.5 29.2
Cellulose 47.2 43.1
Hemicellulose 20.2 4.0
C (wt %) 52.6 55.4
H 5.7 5.1
N 0.2 1.4
S 0.0 0.1
0 (by difference) 38.9 37.8
HHV (MJ kg-1) 20.6 20.3

Basic characterization includes the measurement of particle size distribution, proximate (including moisture content, ash content, fixed carbon) and ultimate analyses (C, H, N, S, O), chemical composition (elemental analysis), cellulose, hemicelluloses, lignin, extractives, and higher heating value. In the case of liquid biomass, (including biomass hydrolysates produced for fermentation and anaerobic digestion substrates,) compositional analysis includes liquid and gas chromatography for sugars, ethanol, specialty chemicals, and fatty acid composition.

Thermal characterizations of biomass include thermogravimetric analysis and differential scanning calorimeter. Thermogravimetric analysis is used to determine temperature points and ranges where devolatilization of biomass occurs. This information is used to measure thermal conversion kinetics and allows the rapid screening of different biomass types before detailed (larger scale) conversion testing, which allows process and product characterization. Differential scanning calorimetry is used to identify exothermic and endothermic reactions, their occurrence points, and magnitude of heat fluxes.

Figure 1. TG and DTG curves showing mass change with time/temperature (mg) and rate of change in mass (mg min-1) for kenaf biomass in an inert (N2) atmosphere

Figure 2. DSC curve showing the cloud point (11.39°C) for poultry fat-derived biodiesel

In our work with microalgae, we have capability to measure chlorophyll content using spectroscopy, and lipid content using gravimetric analysis (ANKOM method).

A significant focus of our efforts is the detailed characterization of intermediates and products of conversion processes used in a biorefinery. In the pyrolysis pathway, biooil (the hydrocarbon rich liquid condensate) and Char (the high carbon solid residue product) are characterized using various methods.

Biooil characterization includes gas chromatograph mass spectroscopy, elemental analysis, viscosity, higher heating value, FTIR, etc. Char is characterized using proximate and ultimate analyses, FTIR, Boehm titration (for estimating surface functional groups), and scanning electron microscopy (SEM). Our advanced characterization capability includes the use of Fourier Transform Infrared Spectroscopy (FTIR) in solid, liquid, and gas phases.

Figure 3. FT-IR spectrum of a catalytically upgraded pine pellet-derived biooil (blue line) compared to a non-upgraded bio-oil (red line)