It is expected that exhaustion of resource caused by population growth and industrialization give rise to various problems including global warming. To solve these problems, it is required various efforts such as reduced consumption of fossil fuels and development of various alternative energy.
Among various alternative energy, biomass is considered the most desirable alternative and attracts public attention as a new renewable energy because it is eco-friendly resources.
In this study, forestwaste was interested as biomass to produce new renewable energy among various materials. To find appropriate conditions of the bio-ethanol production, acid hydrolysis and sugar fermentation experiments were conducted under various conditions.
From the results of acid-hydrolysis experiment, it showed that yield of sugars were increased as raise of temperature, acid concentration and reaction time. It can be found that the optimal conditions for producing sugar from forestwaste, was under 110 ℃, 35 %, and 100 min, respectively. The yield of sugars, which was generated from acid-hydrolysis experiment, was 2.419 mg/gㆍg from softwood and was 1.192 mg/gㆍg from hardwood. Also, it was investigated that acetic acid was more efficient than sulfuric acid for acid-hydrolysis process.
From the fermentation experiment using hydrolyzate neutralized with Ca(OH)2 and KOH, it was shown that S. cerevisiae was more effectively consumed sugars than Y. stipitis and Ca(OH)2 was suitable for corrector. In the results of the experiment using Ca(OH)2, hydrolyzate extracted from woodwaste, which was composed with a mix of softwood and hardwood including larix and polulus, was consumed by S. cerevisiae and Y. stipitis within 24 hours and 72 hours, respectively. From the results of ethanol concentration analysis, it showed that the concentration of ethanol fermented by Y. stipitis and S. cerevisiae was 16.56～27.05 g/L after 72 hours and 20.26～26.78 g/L after 24 hours depending on the mixture ratio of populus and larix, but the concentration gradually became low and it finally showed the concentration of 17.2～23.7 g/L.
Also, it was presented that consuming velocity of sugar using Ca(OH)2 was slightly faster than that of KOH. It probably happened because salt of KOH, dissolved when being neutralized, had an impact on activities of microorganism.
In the results of calculation for the constant of reaction velocity of enzyme by using Michaelis-Menten Kinetics, the maximum values of and was 0.4586 and 1.6921, respectively. As populus was added to the larix, its became lower and became larger, so its constant of reaction velocity became slow. According to this, it was judged that the reaction velocity of S. cerevisiae would be more efficient in production of ethanol than Y. stipitis.
For this study, the possibility of ethanol production from forestwaste was examined. The result of Somogyi Method showed that acetic acid was more efficient in analysis of extraction of sugars than sulfuric acid and softwood released more sugars than hardwood. It was judged that the mixed softwood and S. cerevisiae are more efficient in producing ethanol than hardwood and Y. stipitis. Furthermore, it is suggested that forestwaste could produce ethanol and serve as a new source of bio-energy which could solve the problems such as energy supply and GHG reduction because we could utilize forestwaste.