6 research outputs found
In-situ upgrading of Napier grass pyrolysis vapour over microporous and hierarchical mesoporous zeolites
This study presents in-situ upgrading of pyrolysis
vapour derived from Napier grass over microporous and
mesoporous ZSM-5 catalysts. It evaluates effect of process
variables such catalyst–biomass ratio and catalyst type in
a vertical fixed bed pyrolysis system at 600 °C, 50 °C/min
under 5 L/min nitrogen flow. Increasing catalyst–biomass
ratio during the catalytic process with microporous structure
reduced production of organic phase bio-oil by approximately
7.0 wt%. Using mesoporous catalyst promoted
nearly 4.0 wt% higher organic yield relative to microporous
catalyst, which translate to only about 3.0 wt% reduction
in organic phase compared to the yield of organic phase
from non-catalytic process. GC–MS analysis of bio-oil
organic phase revealed maximum degree of deoxygenation
of about 36.9% with microporous catalyst compared to
the mesoporous catalysts, which had between 39 and 43%.
Mesoporous catalysts promoted production olefins and
alkanes, normal phenol, monoaromatic hydrocarbons while
microporous catalyst favoured the production of alkenes
and polyaromatic hydrocarbons. There was no significant increase in the production of normal phenols over microporous catalyst due to its inability to transform the methoxyphenols and methoxy aromatics. This study demonstrated that upgrading of Napier grass pyrolysis vapour over mesoporous ZSM-5 produced bio-oil with improved physicochemical properties
Soil solarization and sustainable agriculture
Pesticide treatments provide an effective control of soilborne pests in
vegetable and fruit crops, but their toxicity to animals and people and residual toxicity in
plants and soil, and high cost make their use hazardous and economically expensive.
Moreover, actual environmental legislation is imposing severe restrictions on the
use or the total withdrawal of most soil-applied pesticides. Therefore, an increasing
emphasis has been placed on the use of nonchemical or pesticide-reduced control
methods. Soil solarization is a nonpesticidal technique which kills a wide range
of soil pathogens, nematodes, and weed seeds and seedlings through the high soil
temperatures raised by placing plastic sheets on moist soil during periods of high
ambient temperature. Direct thermal inactivation of target organisms was found to be
the most important mechanism of solarization biocidal effect, contributed also by
a heat-induced release of toxic volatile compounds and a shift of soil microflora to
microorganisms antagonist of plant pathogens. Soil temperature and moisture are
critical variables in solarization thermal effect, though the role of plastic film is also
fundamental for the solarizing process, as it should increase soil temperature by
allowing the passage of solar radiation while reducing energetic radiative and convective
losses. Best solarizing properties were shown by low-density or vynilacetate-
coextruded polyethylene formulations, but a wide range of plastic materials
were documented as also suitable to soil solarization. Solar heating was normally
reported to improve soil structure and increase soil content of soluble nutrients, particularly
dissolved organic matter, inorganic nitrogen forms, and available cations,
and shift composition and richness of soil microbial communities, with a marked
increase of plant growth beneficial, plant pathogen antagonistic or root quick recolonizer
microorganisms. As a consequence of these effects, soil solarization was
largely documented to increase plant growth and crop yield and quality along more than two crop cycles. Most important fungal plant pathogenic species were found
strongly suppressed by the solarizing treatment, as several studies documented an
almost complete eradication of economically relevant pathogens, such as Fusarium
spp., Phytophthora spp., Pythium spp., Sclerotium spp., Verticillium spp., and their
related diseases in many vegetable and fruit crops and in different experimental
conditions. Beneficial effects on fungal pathogens were stated to commonly last
for about two growing seasons and also longer. Soil solarization demonstrated to
be effective for the control of bacterial diseases caused by Agrobacterium spp.,
Clavibacter michiganensis and Erwinia amylovora, but failed to reduce incidence
of tomato diseases caused by Pseudomonas solanacearum. Solarization was generally
found less effective on phytoparasitic nematodes than on other organisms, due
to their quicker soil recolonization compared to fungal pathogens and weeds, but
field and greenhouse studies documented consistant reductions of root-knot severity
and population densities of root-knot nematodes, Meloidogyne spp., as well as a
satisfactory control of cyst-nematode species, such as Globodera rostochiensis and
Heterodera carotae, and bulb nematode Ditylenchus dipsaci. Weeds were variously
affected by solar heating, as annual species were generally found almost completely
suppressed and perennial species more difficult to control, due to the occurrence
deep propagules not exposed to lethal temperature. Residual effect of solarization
on weeds was found much more pronounced than on nematodes and most fungal
pathogens. Soil solarization may be perfect fit for all situations in which use of
pesticides is restricted or completely banned, such as in organic production, or in
farms located next to urban areas, or specialty crops with few labeled pesticides.
Advantages of solarization also include economic convenience, as demonstrated
by many comparative benefit/cost analyses, ease of use by growers, adaptability
to many cropping systems, and a full integration with other control tools, which
makes this technique perfectly compatible with principles of integrated pest management
required by sustainable agriculture