Geopolymer foam concrete: An emerging material for sustainable construction

An energy and greenhouse gas (GHG) balance study was performed on the production of the bioplastic polyethylene furandicarboxylate (PEF) starting from corn based fructose. The goal of the study was to analyze and to translate experimental data on the catalytic dehydration of fructose to a simulation model, using the ASPEN Plus modeling software. The mass and energy balances of the simulation model results were then used as inputs for a process chain analysis (by application of the life cycle assessment methodology, LCA) and compared to its petrochemical counterpart polyethylene terephthalate (PET). The production of PEF can be divided into three main units: the production of fructose from corn starch; the conversion of fructose into Furanics and subsequent recovery and upgrading; and the oxidation to the monomer 2,5-furandicarboxylic acid (FDCA) and polymerization with ethylene glycol (EG) into PEF. The ASPEN Plus simulation model describes the conversion of fructose into Furanics, subsequent recovery and upgrading and a CHP unit. The production of fructose from corn starch and the oxidation and polymerization into PEF were based on the literature. In total, six model cases were analyzed, using different sets of underlying experimental data; four cases based on crystalline fructose and two cases on high fructose corn syrup (HFCS). Fructose can be converted into Furanics at efficiencies between 38% and 47%. The production of PEF can reduce the NREU approximately 40% to 50% while GHG emissions can be reduced approximately 45% to 55%, compared to PET for the system cradle to grave. These reductions are higher than for other biobased plastics, such as polylactic acid (PLA) or polyethylene (PE). With an annual market size of approximately 15 million metric tonnes (Mt) of PET bottles produced worldwide, the complete bottle substitution of PEF for PET would allow us to save between 440 and 520 PJ of non-renewable energy use (NREU) and to reduce GHG emissions by 20 to 35 Mt of CO2 equivalents. If also substantial substitution takes place in the PET fibres and film industry, the savings increase accordingly. The GHG emissions could be further reduced by a switch to lignocellulosic feedstocks, such as straw, but this requires additional research.

Replacing fossil based PET with biobased PEF; process analysis, energy and GHG balance

This article defines sustainability and sustainable cyclic processes, and quantifies the degree of non-renewability of a major biofuel: ethanol produced from industrially grown corn. It demonstrates that more fossil energy is used to produce ethanol from corn than the ethanol's calorific value. Analysis of the carbon cycle shows that all leftovers from ethanol production must be returned back to the fields to limit the irreversible mining of soil humus. Thus, production of ethanol from whole plants is unsustainable. In 2004, ethanol production from corn will generate 8 million tons of incremental CO2, over and above the amount of CO2 generated by burning gasoline with 115% of the calorific value of this ethanol. It next calculates the cumulative exergy (available free energy) consumed in corn farming and ethanol production, and estimates the minimum amount of work necessary to restore the key non-renewable resources consumed by the industrial corn-ethanol cycle. This amount of work is compared with the ma...

http://alpha.chem.umb.edu/chemistry/ch471/evans%20files/Patzek.pdf

Thermodynamics of the Corn-Ethanol Biofuel Cycle

Forest and bioenergy strategies offer the prospect of reduced CO 2 emissions to the atmosphere. Such strategies can affect the net flux of carbon to the atmosphere through 4 mechanisms: storage of C in the biosphere; storage of C in forest products; use of biofuels to displace fossil-fuel use; use of wood products which often displaces other products that require more fossil fuel for their production. We use the mathematical model GORCAM (Graz/Oak Ridge Carbon Accounting Model) to examine these mechanisms for 16 land-use scenarios. Over long time intervals the amount of C stored in the biosphere and in forest products reaches a steady state and continuing mitigation of C emissions depends on the extent to which fossil fuel use is displaced by the use of bioenergy and wood products. The relative effectiveness of alternative forest and bioenergy strategies and their impact on net C emissions strongly depend, for example, on the productivity of the site, its current usage, and the efficiency with which the harvest is used. When growth rates are high and harvest is used efficiently, the dominant opportunity for net reduction in C emissions is seen to be fossil-fuel displacement. At the growth rates and efficiencies of harvest utilization adopted in many of our base scenarios, the net C balance at the end of 100 years is very similar whether trees are harvested and used for energy and traditional forest products, or reforestation and forest protection strategies are implemented. The C balance on a plantation system that provides a constant output of biomass products can look different than the balance of a single parcel of land.

K. Vringer

Papers

New gross energy-requirement figures for materials production