Download Mode of Developing New Energy Sources: Garden Waste to Produce

EASTERN ACADEMIC FORUM
Mode of Developing New Energy Sources: Garden Waste to Produce
Ethanol Technology
LI Zhi, SUN Lijun
School of Economics and Management, Beijing Forestry University, China, 100083
[email protected]
Abstract: Nowadays the main processing methods about the garden waste recycling, such as
incineration, landfill, composting, and rough, still have some defects and problems. On the basis of
extensive experiments on the garden wastes, we are introducing a new technology to produce ethanol by
garden waste ,which can not only make full use of garden waste and reduce maintenance costs of urban
greening, but also provide a new energy development model, and to a certain extent, ease the energy
crisis our country. It has enormous economic, social and ecological benefits.
Keywords: garden waste, garden waste for ethanol production technology, new energy development
model
1 Introduction
Garden plants garden plant waste mainly refers to natural or artificial pruning litter produced by the
plant debris, including wastes, clippings, pruning trees and shrubs, with its main components of wood
fiber [1]. With increasing urban green coverage, the number of garden waste growing day by day , if we
don’t treat it seriously, it will not only affects the appearance of the city, but also cause environmental
pollution. At present the basic approach is incineration, landfill, etc. Chen Xiang, Xian Xudong, Bao
Bing (2009) held the view that landfill or incineration will cause environmental pollution and resource
waste, and proposed other approaches like compost, green coverage and utilization of product
development approach [2]. Lv ZiWen, Fang Hailan (2007), Liang Jing (2009), Yang Hui (2010)
introduced landscape waste treatment and disposal methods in U.S specifically, such as compost
proportion, composition and classification, collection methods, optimization of composting process
parameters (e.g.particle size, humidity, carbon and nitrogen ratio and pH value, etc.), standards of
product quality and technical specifications and so on, they proposed some recommendations such as
classified collection of garden waste and garbage, set up a special court for smashing the branches,
compost to field and so on [3-5]. Beijing, as the country's capital, its green coverage had straight up in
recent years, and in 2007 reached 43.0%. With the acceleration and expansion of green field,
landscaping waste has become a huge source of pollution to urban environment. In 2007, Beijing
generated 2.36 million ton landscape waste, most of which was landfilled as a solid waste, and the
resource re-utilization rate is only 0.7%. In this regard, Yu Xin, Sun Xiangyang, Xu Jia (2009), through
surveys, made an empirical analysis of the landscape in Beijing and its re-use of waste, presented three
approaches, that is ,the re-use composting, production of new flowers matrix, covering the production of
organic gardening. [6]
Developing new energy, carrying out industrial revolution, is an effective way to achieve sustainable
development and a low carbon economy [7-9]. In a variety of new energy, biomass attracted the attention
of many scholars, Dong Youfu, Hou Fang’an (2007) and Liu Jianfu, Bai Yurui (2009) held that with the
deterioration of the global environment and energy crisis, renewable energy represented by enhanced
solar and biomass had increasingly become the focus of attention, so we should be fully aware of the
value of crop straw, and promote the comprehensive utilization of straw [10, 11]. LiTao, Zhuo Haifeng
(2008) describes the environmental pollution and resources waste caused by incineration of straw, and
proposed several measures such as straw Production of feedstaff, straw processing, gas producing [12]. As
for the way of straw utilization, scholars also discussed. Zhang Zhenhan (2006) proposed the straw
power generation and plate-making technology [13]. Xie Zuqi, Liu Jianhui (2007) proposed straw
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gasification technology [14].
Can we combine garden waste disposal and new energy development together and propose a new
low-carbon economy model to make full use of the biomass energy of garden waste? There are still no
such studies. So, through the analysis of the experimental on the garden waste such as weeds and
sawdust, we are exploring the this new energy technology development ,which is to use garden waste to
produce ethanol.
2 The Status of Garden Waste Recycling
United States, Canada, Belgium and Australia and other countries have made a very good use garden
waste so far. In the U.S., urban greening has come out of the traditional methods and been replaced by
producing renewable soil, compost instead of natural soil in city greening. Many studies in United States
have shown that the re-use of garden plant waste is more economical and more environmentally friendly
than landfill and incineration. According to statistics, the cost of puting garden waste into landfill is 350
dollars, the carbon dioxide produced by the burning of garden waste a ton is 230 kg, so many states in
US have enacted laws relating to the funding security measures to implement garden waste recycling.
Because of the protection policy and funding, the garden waste recycling ratio in the United States
increased each year from 12.4% in 1990 to 62.0% in 2005.
In 2007, Chao Yang District in Beijing established the first domestic large-scale professional garden
plant waste disposal site. After reduction treatment and a series of manufacturing processes, waste
disposal sites can produce the necessary bio-organic fertilize, organic substrates ground cover and other
products in the urban greening. In addition, Guangzhou, Shenzhen and other economically developed
regions have started the garden waste recycling as well. Management Office in Shenzhen City has been
operating for 11 years since 1998. The amount disposed by the Crush site is very large,
3 The Problems of Current Methods
Current treatment of plant wastes are incineration, landfill, composting, and rough and so on.
3.1 Incineration
Burning garden wastes can produce large amounts of harmful gases (such as nitrogen oxides), which
pollute the atmosphere. Besides, it can bring a large number of carcinogenic particles (such as dioxin,
trip-benzopyrene and quadr-benzopyrene), which do harm to human health, so this kind of approach has
been gradually prohibited in recent years.
3.2 Landfill and composting
Landfill disposal and composting wastes is still the common means. Composting refers to the
occurrence of biochemical degradation and the formation of organic fertilizer by the use of
microorganisms in a certain temperature, humidity, pH and other conditions. Garden organic waste is
rich in N, P, K and other nutrients. Through composting and other treatment ,it can be used as fertilizer
in the soil, which can effectively restore soil nutrients, increase soil organic matter content, stimulating
microbial activity, improve soil physical structure and chemical composition, increase soil porosity, and
enhance soil capacity to retain water and fertilizer. At present, major cities such as Shanghai, Beijing,
Guangzhou and Shenzhen, have started composting of the garden waste.
However, as garden wastes contain less water and are light in weight, the transport and removal costs
may increase through the landfill. In addition, landfill and composting sites need a large space and a
long fermentation period and the degradation and transformation is not complete, this method will not
only bring about secondary pollution, but also lead to other security issues.
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3.3 Plate
National attitudes to protect forest resources become increasingly clear, measures such as cutting of
forests to limit and logging ban have been taken more seriously. In next few years China's timber
harvesting will be reduced to very low commodity level, plate production industries face enormous
challenges and the supply of raw materials will become a bottleneck. To find new materials to replace
natural wood may be a way out. Wastes after rough handling, can also be pressed into sheets, but these
plates crushed by garden wastes are of loose granular material and are poor in bearing pressure, so there
still be some challenges in their use and consumer acceptance.
3.4 Feed production
Lawn can be collected and dried into hay or made into feed. However, because plant wastes and weed
contain tannin, which may cause animals’ resist. Besides, the green wastes are of lower protein content
and lack in vitamins, so the bioavailability is poor and thus should not be used as the feed directly.
4 Garden Waste to Produce Ethanol Technology
Because of the intensification of the global energy crisis, many countries are devoted to the development
and utilization of renewable energy. Biomass energy gets people's special attention for its cleanliness
and extensive usage. Bran, straw, chaff, weeds and industrial waste, sawdust and other celluloses has not
been fully utilized except that a small amount of them are made for paper. According to foreign statistics,
the total output accounts for approximately 50% of biological resources and adds up to100 ~ 50 billion t
a year. The fermentation process of weed to produce fuel is shown in Figure 1.
Garden wastes
e.g. weed
Sulfuric acid
Ammonia
Cooking and steaming
SQY-1
Ethanol
H2O
SQY-2
Filtration
Liquid-state
fermentation
Filtrate
Filtrated waste
Distillation
Cellulose enzyme
Waste liquid
SSF
rectification
Yeast
Solid state
distillation
Waste
residue
Ethanol
Figure 1 Fermentation process to produce fuel ethanol
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4.1 Cooking and steaming
As shown in Figure 1, mix the weed and 1% of sulfuric acid by a certain rate(solid to liquid is 1:10) at
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for 120min, then filtrate and wash it by hot water, which weighs 4 times of that of garden
waste .As the filtrate contains some sulfuric acid, the filtrate was re-pumped back to the cooking pot,
and the waste into the solid-state fermentation pot (control the residual acidity is about pH4.8). In
continuous operation, when the system starts, add 1% of sulfuric acid. Once the operating system
running continuously, we can control the acidity by adding a small amount of concentrated sulfuric acid
through the cooking process.
℃
4.2 Fermentation and distillation
When the concentration of reducing sugar in the filtrate reaches 5%, put some filtrate into the cooking
pot, and others into the fermenting tank , and then cool it with ammonia or the neutralization of
ammonium bicarbonate and sulfuric acid in the pot. As the reducing sugar in the hydrolysis fluid during
the pretreatment of corn by dilute acid is mainly xylose, put activated SQY-1 which can ferment pentose
to produce alcohol in the fermentation tank and start the fermentation at a stirring speed of 80r/min for
48h. When fermentation is completed, put the fermented liquid into the distillation of crude distillation
tower, and we will get alcohol at the concentration of about 50% (v / v).
4.3 Fermentation and distillation in solid state
Solid-state fermentation (Solid-state fermentation, referred to as SSF) refers to the transformation
process of the biological raw materials without free water by micro-organisms. The traditional
submerged fermentation (Submerged fermentation) is to use the diluents or suspension of raw materials
for fermentation. In the SSF process, there is usually a thin layer of water on the surface of the solid
matrix and the weight ratio of water and solid substrate is between 4:1and 6:1 on average. Compared
with submerged fermentation, the advantages of SSF are: less volume of the fermentation vessel; less
energy costs of sterilization; more easily ventilated in solid substrate; less capital spending or operating
expenses in wastewater treatment; less costs in the products collection and feed drying; less risk of
bacterial contamination for it is less conducive to bacteria’s growth; in Add the solid residue(weighed as
25IFPU / g dry matter) into cellulase, and activated high-temperature yeast SQY-2 as well, then start the
solid-state static fermentation after an even mixing. Take CO2 out during the process to control the
temperature, the amount of oxygen dissolved and the heat loss. After 60 hours’ fermentation and the
process of solid-state distillation, we can obtain 50% (v / v) alcohol.
4.4 Rectification
Rectify the alcohol distilled from SSF and the distillated liquid to obtain 95% (v / v) alcohol, and the
alcohol obtained can be used as fuel to solve the current energy crisis.
4.5 SCP production
As the liquid waste contains large amounts of distilled NH4 +, you can use it to produce feedings SCP.
Mix the liquid residue distillery waste with the solid ones, access yeast to produce SCP, which can not
only solve the environmental pollution problems, but also realize the comprehensive utilization of
agricultural waste.
5 Conclusion
Garden waste recycling is an effective approach to achieve scientific development in landscape greening
and zero emissions in garden waste, which is consistent with the sustainable development. Using such a
new technology as Garden waste to produce ethanol can achieve the unity of ecological, social and
economic benefits .As a result we should spread it in the process of new energy development, in order to
better deal with the problems in the recycling of garden waste and promote the exploration of new
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energy and development of low carbon economy.
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