Biomedical Engineering Reference
In-Depth Information
There are still many problems using straw and other lignocellulosic resources
to produce biofertilizer, such as the low degree of mechanization and the low
substrate conversion rate, which seriously affect the effective use of straw organic
fertilizer. Therefore, vigorous development of the combination of mechanization
and biotechnology will resolve the problem of straw returning effectively.
5.2.1.4
Other Fertilizer
(1) Humic acid fertilizer
Humic acid fertilizer is a new type of fertilizer containing humic acid substances.
The main categories of humic acid fertilizer are humic acid, nitro-humic acid, and
purified humic acid products. The first two are usually mixed with nitrogen, phos-
phorus, potassium, and trace elements to prepare humic acid compound fertilizer,
mainly used as base fertilizer. Purification of humic acid is mainly used for irrigation
or spraying of crops as a growth regulator and is also used for soaking of seed to
improve germination and encourage a strong sprout. Humic acids show a wider
application in the fields of industry, agriculture, animal husbandry, and medicine
in China. The traditional humic acids are prepared using coal resources as raw
materials, which means humic acids are obtained by consuming nonrenewable coal
resources. Other individual manufacturers produce humic acids by microorganism
fermentation using agricultural by-products as raw materials. However, the cycle
of microbial fermentation production is long, and the products are not stable. Chen
et al. invented a method to produce humic acid by steam-exploded straw using straw
as raw materials. The technique was to load the straw into a steam explosion tank
and then explode the raw materials with steam pressure to obtain steam-exploded
straw containing humic substances. After recovery, fulvic acid and humic acid are
mixed by soaking the steam-exploded straw with alkaline solutions. The principle of
this method is that, in the cooking process, the reactivity of lignin increases because
of the cleavage of part the ether bond of lignin and leads to the formation of humic
acid substances by the reaction of lignin and the nitrogen-containing compounds,
ash, and sugars from hydrolysis of hemicellulose [
38
].
(2) Ecological fertilizer from-steam exploded straw
The traditional process for prepare fertilizer, including explosion of straw at high
temperature and high pressure, composting under natural conditions, and mixing
with inorganic fertilizers shows some disadvantages: The sugars hydrolyzed by the
treatment with explosion under high temperature and high pressure are wasted and
pollute the environment; the organic matter conversion rate is still low; this fertilizer
is from inorganic fertilizer, and the straw just plays the role of carrier. Because of the
shortage of existing technology using straw to produce organic fertilizer, Chen et al.
provided a method to prepare ecological fertilizer using steam-exploded straw as
raw materials for solid-state fermentation to achieve ecological regulation of soil
quality and beneficial microbial populations and prevent fertilizer pollution and
waste [
39
].
