Agriculture Reference
In-Depth Information
managements, soil moisture, type of fertilizer, timing, and so on. By the way, on the base to
the literature evidences exposed before, some guidelines of the better management practices
(BMPs) can be identified and summarized.
Snyder et al. (2009) reported four guidelines in order to optimize N fertilizer use in
agriculture:
1)
when fertilizer is used to increase crop yields, it increases the efficiencies of other
energy-consuming inputs used in production. However, since fertilizer use itself
involves energy consumption, the importance of applying the optimum rate is
underscored.
2)
by increasing the net primary productivity of cropland, fertilizers can increase the
return of C to the soil as crop residues, mainly as root biomass and rhyzo-deposits.
3)
since demand for biofuels increases the need for higher biomass production per unit
of land area, it also increases fertilizer use. If the goal is net energy production or
fossil fuel offset, this fertilizer use must be efficient.
4)
when fertilizer is used to increase crop yields, land for forests and other natural areas
can be spared from conversion to cropland.
Several studies explored the possibility to produce fertilizers based on renewable
resources. Ahlgren et al. (2008) have studied the use of hydrogen from gasified biomass for
the production of ammonia (cereal straw and short rotation willow (
Salix
) coppice) with a
reduction of greenhouse gas emissions compared with using natural gas. Indeed, the main
energy requirements for fertilizer production are due to fuel and feedstocks used in the
manufacture of ammonia (Spinelli et al., 2013b). On the contrary, eutrophication potential
was higher in the biomass systems due to nutrient leaching from soil and the acidification was
in the same range for both natural gas and biomass (Ahlgren et al., 2008).
Another possibilein obtaining hydrogen is to produce methane by anaerobic digestion of
several type of biomass (Collet et al., 2013; Show et al., 2012) and then produce hydrogen
from the methane gas. Other aspects that should be considered are the following (IFA, 2009):
•
improving energy efficiency in ammonia production because the coal-based
ammonia synthesis, especially for the China policy, is expected to increase in coming
years and carbon capture and storage could be used to reduce the emission;
•
reducing nitrous oxide emissions in nitric acid production by secondary catalytic
processes to convert 70-95% of N
2
O into dinitrogen (N
2
) and water without
additional energy use;
•
reducing greenhouse gas emissions related to transport and logistics because the
future growth is expected where trucking is the primary way for the distribution
(Asia, Africa and South America);
•
using fertilizer best available management practices to improve agricultural
greenhouse gas balances.
The first fundamental choice is the use of the best N source and rates (avoid excessive N
applications) for the specific crop and pedo-climatic conditions, in order to improve N crop
nitrogen uptake by crops, thereby reducing the N loss via soil microorganisms transformation,
as well as in reactive forms. This choice is strictly connected with timing N supply, planned
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