Biomedical Engineering Reference
In-Depth Information
Researches on artificial vegetation in China began in the late 1990s; it started later
than in foreign countries, but with similar production technology to those countries,
mainly blanket-like or ribbon products produced using natural fibers such as straw,
coconut shell, a variety of hemp, and so on as the raw material and then mixing with
seeds, fertilizers, and net in certain proportions. However, the low-technology level
results in low mechanization and efficiency of artificial vegetation, which further
limits its application because of the high costs compared with traditional greening
technology. The renewable fibers are used to produce nonwoven fabrics, and plant
seeds are mixed with fertilizers and pesticides, although in certain roles, extensive
use would pollute the environment and groundwater [
20
]. Some products take waste
newspapers, waste cotton, and wastepaper as carriers and then add the seeds and
fertilizers into them, but these untreated urban wastes are resistant to degradation
resulting in the low use value, but some heavy metals in them would massively
accumulate to cause pollution of the soil environment [
21
]. Coconut also can be a
belt-seeding carrier; the seeds and water-retaining agents are adhered in meshes of
coconut, but the product nutrient contents are low, and the seed germination cycle is
long; the germination rate also is not high [
22
].
On the problems of the high cost of existing artificial vegetation technology and
the product effects that are not obvious, with the products unsuitable for a large-
area spreading application, Chen et al. [
23
] provided a preparation method of belt-
seeding carriers via solid-state fermentation of steam-exploded straw that can avoid
or significantly reduce the use of pesticides and chemical fertilizers, decrease the
amount of original carrier materials and additives, and effectively lower the cost
and environmental pollution.
This method takes straw, the waste of the agriculture industry, as the main
carrier; it uses steam explosion to humify straw and lowers the crystallinity of
straw, increasing water absorption and degradation. Steam-exploded straw is washed
and divided into washed matter and water-washed liquid. Through the solid-state
fermentation of the complex microbial system in washed matter, carriers have the
effect of biofertilizer and disease resistance. Xanthan gum, the fermentation product
of water-washed liquid, can be used for adhesion of carriers and seeds and shape
forming of the carrier. This technology has some advantages; for example, there is
no need for additional pesticides and fertilizers, reducing the amount of retaining
agents and adhesive, decreasing the demand of fine soil and the cost of construction
and management, and promoting the protection of the environment.
The technical route of belt-seeding carrier preparation via solid-state fermenta-
tion of steam-exploded straw can be described as follows:
(1)
Preparation of seed liquid of a single bacterial strain
. Whole straw is cut to
3-5 cm, then water with the same weight of raw materials in it is added to infiltrate
the straw for 10-15 min. Next, put the material into a steam explosion tank, input
the high-pressure steam, and maintain the pressure in the steam explosion tank at
1.3-1.6 MPa for 5-7 min. Quickly open the outlet valve to release the pressure, and
the steam-exploded straw is discharged from the discharge port.
