هذة مقالات بالغة الانجليزية عن الرى - والتربة - التجفيف - القص - الامراض
CONTENT1.0 PRODUCTION OF PAULOWNIA FOR BIOMASS1.1 Choosing a place1.2 Reqirements of Paulownia for the soil, climate and agronomicalconditions.1.3 Instructions for soil sampling for soil analysis.1.4 Planting material1.5 Planting and looking after – general conditions1.5.1. Preparation of the land1.5.2. Rain and wind1.6 Planting1.6.1 Pastures and lands covered with bushes1.6.2 Bushes control after planting1.6.3 Trench1.6.4 Disking /leveling/1.6.5 Furrowing and marking1.6.6 Determination of the seeding scheme1.6.7 Watering1.6.8 Fertilising1.6.9 Paring1.6.10. Planting without complete treatment of the soil1.7 Diseases and enemies1.8 Yields1.9 Harvest1.9.1 Direct harvest of chips1.9.2 Harvest of whole stems1.9.3 Harvest of sticks1.10 Drying and storage1.11 Restoration of the land2.0 ECONOMIC APPLICATION2.1 Burning, Gazification and Pyrolysis2.2 Bioremediation2.3 Costs and economic evaluation3.0 ENVIRONMENTAL IMPACTS FROM THE USES OF PAULOWNIA3.1 Flora3.2 Invertebrates
Introduction
World petrol and gas reserves are decreasing and their yield, deliveries and high
interest are making the final product too expencive. Bulgaria and central
Europe generally are having limited stocks of similar energy sources and they
are importing the bulk of their needs. When it is about petrol this is near 100 %,
in the cases about gas it is the same. If we make a conclusion this is going to be
an almost full dependence from external sources that could not be influenced.
Europe is facing the challenge of the climate change, the increasing dependence
of importing resources and energy and the rising energy costs.
In this condition the European aims for sustainable development are becoming
more difficult for achieving. The new European energy policy, in particular – and
the national, aim to overcome these challenges for the benefit of all European
citisens. The starting point of the European energy policy is at the tree priority
directions:
Mastering the negative climate changes;
limiting the external dependence of EU of imported energy
resources;
encouragement of the economi cal growth and
employement and thi s way i t wi l l as sur ing secure
and af fordable energy for the user s ;
Achieving these goals is impossible without the development and the use of a
wide range of renewable energy technologies – wind, solar, hydro, tidal and
thermal. The biomass from energy cultures that have a particular application in
Bulgaria are at the developpment stage where they are ready for commercial
application.
Renewable energy
The renewable energy sources are providing sustainable and carbon neutral
natural source of heat or energy, as well as improving the security and the
divercity of the deliveries of energy sources.
Some types of renewable energy are having the potential to create and sustain
significant employment in the economical regions. The main limitations with
the renewable energy sources are linked to the consumers confidence and
with the reliability and delivery (due to the nature of some of the sources for
example wind), as well as the costs for the construction that are
reflecting at the energy supply prices. The increasing interest into the
renewable energy and the forecasted potential is a result of multiple factors:
The world conviction that the levels of the carbon emissions needs
immediate decrease for reducting their effect over the global
warming;
This has led to the entry of many international binding instruments
under the Kyoto Protocol limiting the levels of carbon emissions to
certain levels up to 2012. In the European Union the binding norms
will continue to be valid even after Kyoto;
The decreasing reserves and the increasing prices of the fossil
energy sources, particularly gas, petrol and their sensibility to
political influences.
The need to reduce according to the energy import needs by
reliable supplies that the local sources can provide;
The extremely vulnerable position where the conventional
agricultural production is in at the overall economy of the country
and the press on her by multiple countries are urging to alternative
and sustainable possibilities for the use of the land such as the
growth of energy crops.
Big part of the potential that the biomass from energy cultures have in the
reduction of carbon emissions is coming from:
Displacement of the fossil fuel sources for heating as a beginning
and subsequently with the development of the technologies for
small and medium-sized power plants for electricity production.
The neutral status of the biomass from energy cultures regarding
to The C02 emissions, when the growing culture consumes as much
as atmosphere carbon dioxide that subsequently is being released
in the convertion and into the renewable energy as heat or
electricity.
The total carbon cost has been calculated for the production of
energy from biomass, gas and coals and shows the emissions of
CO2 from 60g, 400g и 1,000g for kW electricity respectively.
Biomass
All the the sustainable energy sources are entirely obtaining its energy from the
sun except the tidal and geothermal ones. In the case of energy cultures from
biomass the solar energy is transformed by the plant into a chemical energy
stored in the biomass through the natural process photosynthesis. This could
be oils or oilseed crops, the grass Miscanthus (elephant grass) or under the
shape of wooden biomass for the species with short rotation period such as
Paulownia, poplar or willow whose stems are going to be cutted. The wooden
species represents 60% of the total yield of biomass and Paulownia turns out to
be the most effective culture for our lattitudes comparing its year yield from
with the one from poplar, willow or Miscanthus.
The main advantage of Paulownia as an energy crops is the rapid growth in the
first 1-2 years of its development and the ability of its root system to maintain
the formation of new plants at the place of the trunk.
The material will be planted in the spring as at the end of the first vegetative
period it shall be cutted at ground level in order to provoke the next year
formation of multiple new stems. The growth in the next year is rapidly reaching
3-4 metres untill the end of the year and more than 6-7 metres in the second
year when it will be cutted for processing of the produced biomass. A similar
plantation can live 20-25 years and suggests 10-12 harvests, after that the land
could be reused for another application.The expected quantity of the yield per
acre is different according to few factors. At first comes choosing the kind,
place, climate factors, additional irrigation and all the others factors affecting
the traditional crops. The expected yields of Paulownia could vary within the
range of 30-40 tdm/ha/y or in two years rotational cycle up to 80 tdm/ha.
Measured in units of energy the dry mass from Paulownia has energy content
about 18MJ energy for a kilogram 42% from the energy in equivalent volume
of light fuel. This wat we can recalculate the yield per hectare per year
equivalent to 12 000- 17 000 l i t res fuel f rom hectar and f rom here
we can easi ly evaluate the yield f rom Paulownia in f inancial
equivalent .
At this background there is an expectation on the prices of the fuels that they
will gradually continue to grow and an investment in an energy crop like
Paulownia is really reasonable.
1. PRODUCTION OF PAULOWNIA FOR BIOMASS
1.1 Choosing the site
The downmentioned climatic, geographical and biological requrements of
Paulownia are intended to guide investors to the appropriate growing energy
crops on his choice for the plantation site.
Paulownia grows up to 2000м altitude and latitude 40оN и 40оS. For
husbandry with investment purposes is recommended the latitutde
do be less than750m – 800m.
The growth of the trees starts in the spring, when the temperature of the soil is
reaching 15оС -16оС. Opt imal temperatures for Paulownia’s growth are
in the range of 24оС -33оС.
Paulownia is highly adaptive to diverse soils and grows at a wide range, but the
best development could be seen with deep and well drained soils. The best
and preferred for raising Paulownia are the light aerated and sandy soils
without slope.
Unappropriate for ras ing Paulownia are the clay, rocky, podzolic and soaked
(swamped) soils. Soils that contain clay more than 25% and porosity under
50% are not appropriate for growing Paulownia.
Good growth of Paulownia is observed wi th soils having a рН from 5.0
to 8.9. Paulownia can not tolerate soil salinity more than 1%.
1.2 Requirements of Paulownia for the climatic and agronomic conditions.
Paulownia is highly adaptive tree species, but in order to ensure the
economical effect of the plantation and a hight yield if quality timber you have
to provide the following: appropriate soil, climate and agrotechnical conditions.
parameter Limits
Mechanical composition, cont. of physical clay up to 30 %
рН 5,00 – 8,50
Content of water-soluble salts under 1 %
Power of the profile above 90 сm
Power of the humus horizon above 40 сm
Total porosity under 50 сm
Soil density about 1,3 g/сm3
Height of groundwaters under 2,00 m
Altitude up to 800m
Average year temperature 13 – 25 0C
Max Т С0
+40,0 0C
Min Т С0
-24,0 0C
Rain, mm/month above 150 mm/month
Wind speed up to 28 кm/h
Light norm 20000 – 30000 lu
1.3 I n s t r u c t i o n s for soil sampling for soil analysis from areas intended
for Paulownia cultivation.
Basic requirement
The soil sample should be representative for the area where it was taken. For
this purpose it is necessary to take an average sample of each area, regardless
its size. If the size is more than 10 ha, an average soil sample has to be taken on
every 10 ha – so called elementary section. At slopes there are formations of
elementary sections in the upper, middle and down part of the field.
Collecting the first average samples has to be performed during normal
meteorological conditions.
1.4 Planting material
Choosing the planting material has a key role for ensuring the economic
impact of a plantation for biomass. The main criterias are the temperature
regime and the rainfalls. Theese are the two main requirements for the
choice of planting material. BIO Tree company suggests the hybrid kinds
expressly selected for biomass yield. The hybrid varieties selected in Bio
Tree company are appropriate for: yield of high quality timber – kind
Bellissia and for biomass production – kind Oxi.
1.5. Planting and growing – general conditions
1.5.1. Site preparation
Usually Paulownia is planted during spring and mid-summer in
dependence of the development stage of the planting material /one year
old saplings or young planting material/ and prefers horizontal or south
orientated slopes. As all young trees, Paulownia plants should be well
protected from herbivorous animals.
1.5.2. Sun
Paulownia requires a lot of sunlight for its best growth.
1.5.3 Rain
Irrigation is necessary if during the first vegetative period the rain is less
than 150 mm per month. In comparison 10mm of rain delivers 10 liters of
water. Watering is needed in the following years if the monthly rainfall is
under 50mm. Insufficient watering slows the growth but does not kill the
plant.
1.5.4 Wind
Plantation is good to be placed in areas without strong winds reaching
over 28km/h. When there are powerful winds at the place of planting
stabilizing post has to be put during the first year of development until
they form strong wooden stem. The speed of the wind is dangerous for
the young plants over 45km/h and such areas have to be avoided.
1.6.1. Pastures and lands covered with bushes
When selecting a pastures and meadows for plantation with Paulownia,
the terrain has to be pre-treated with herbicide at least 4-5 weeks before
planting. The adherence of thit period is required by the necessity of the
full degradation of the traces from the herbicide in the soil and not to
harm the young and fragile plants. The Herbicide must be choosen to be
able for removal after and to provide long – lasting control for at least 9
months.
The terrain shall be cleaned before the planting and any re-growth of the
weeds must be strictly controlled.
1.6.2. Control on the weeds after planting
Control over the weeds is helping the growth and the virality of the plant.
A circle with diameter 1.5 m around every single tree shall be maintained
without any weeds at least for the next 2 years. Springtime you have to
spray just before the beginning of the growth (waking up), but you should
escape a contact with the stem of the tree. If young rooting cuttings
appears around the tree they must be removed by hand and not by
herbicide.
1.6.3. Trench
Before planting it is recommended plowing the land /minimum at 40 – 60
cm/ aiming to crush the soil and to remove the roots of the perennial
weeds and bushes. If the soil is heavy and clay the trenching shall be at
the depth of 70сm - 80 сm.
1.6.4. Disking /leveling/
After trenching it is necessary to level the land two times. After that it
could be considered that the land is prepared for furrowing, marking,
planting.
1.6.5. Furrowing and marking
The furrowing is performed at the depth of 20 cm. After that you have to
mark the planting spots. In every single planting spot you have to put
additional fertilizer or manure that is mixed with soil in advance. The tree
is planted in a way that the connection between the stem and the root to
be of moisture saturation of the soil during the winter it is recommended
to build a mound (pile), so the level of the soi l wi l l increase at
the plant ing spot . It is appropriate the mound to be 25сm -30 сm
higher than its surrounding soil.
1.6.6. Determining the planting scheme
Paulownia for timber production – When creating a plantation for
timber we recommend the planting scheme with 4х4, 5х5 meters or 5х4
meters between the trees which means 500 or 600 trees per hectare.
Larger density leads to competition for area between the trees and slower
their growth after the first 3-4 years. Lower density leads to faster initial
growth which lowers the timber quality. Higher density does not lead to
commercial effect, the necessity of elimination of plants is connected with
expenses for eradication and herbicide treatment to stop the regeneration
from the roots and in the end the 3-4 years old stems does not possess
enough volume to be used for timber.
Paulownia for biomass – For effective yields we recommend the trees to
be planted with higher density than the one used for timber production.
The density should be between 3500 and 10 000 plants per hectare which
depends on the rotation cycles of for the biomass collection strongly
linked with the purposes of the biomass (pellets, chips, bioethanol,
fodder) and the harvest machines.
1.6.7. Irrigation
It is recommended before planting to irrigate well the terrain. The
saplings shall be irrigated at the day of their planting and after that, until
they develop a strong root system (about 2 years). The second
irrigation shall be 2-4 days after their planting. Irrigation after planting
shall be regular and amply, especially in a dry season. Irrigation is
necessary if the rain during the first vegetative season is not
less than 150 mm per month. It is also necessary in the following
years if the monthly precipitations are less than 50 mm.
The regular development of Paulownia requires :
or rains with with relatively equal alignment - minimum 120 - 150
mm per month irrigation /drip /and/or subsoil moisture at
the depth of 11.5 m.
The main requirement for maximum growth is the regular and amply
irrigation at a time of the vegetational period.
1.6.8. Fertilising
Paulownia is tolerant to poor soils and could reach acceptable dimentions
for the stem diameter. Paulownia thought, grows much better in fertile
soils. The experiments shows that the best is to apply the fertiliser under
the form of nitrogen, phosphorus and potassium at the time of planting.
Nitrogen is more effective, when it is applied as an independent element.
Sometimes it is necessary to fertilise the soil at the time of planting, but it
is strictly in accordance with the results of the soil analysis.
If preliminary soil analysis has not been performed you can do feeding up
by the following materials and start up nutrients:
- soil: organic fertiliser - 1 : 1
- triple superphosphate /TSP/ - 200gr
- potassium phosphate - 120gr
- ammonium nitrate - 150gr
During the exploitation of the plantation the soil is getting poorer and you
have to keep that in mind. Because of that it is necessary to use an
additional fertilisers during certain periods. The duration of the periods
depends on the basic position of the soil and also on the growth rate and
the rotation cycles of the plantations. It is recommended after the first
rotation cycles to monitor the amount of nitrogen, potassium and
phosphorus in the soil, after a scheme for alternate loading has been
issued.
1.6.9. Pruning
The goal of raising Paulownia is to produce a good crop of trees possessing
a good shape and in a good condition. This could be achieved by
for stimulation of the development of maximal quantity timber witout
wooden knots on the tree trunk. This could be achieved by removing the
branches, that are not having big importance in the maintenance of and
optimal leaves number needed for the photosyntetic activity.
1.6.10. Plant ing wi thout complete t reatment of the soi l
/it is allowed only in the cases when the complete treatment of the soil, forestation in a
forestry fund, decoration of parcs and gardens are not possible/
If for any reason you have to plant Paulownia without any treatment in
advance it is necessary to plant the plants into holes, previously
excavated.
Firstly the planting spots shall be marked, after the holes shall be
excavated. If the land is not loose, the holes shall be as wider as they can
be /for heavy soils it is obligatory/- at least 60х60х60 сm. The top soil
shall be separated from the bottom soil in the process of
digging. After that the hole shall be half filled with topsoil (it is
recommended to mix with organic fertiliser).
The plant shall be planted in a way that the connection between the
stem and the root will be about 1 cm below the ground level. The left soil
is superimposed and rammed. At a flat land, especially if there is a risk
of saturation of the soil during the winter is recommended to build a
mound (hillock), so the soil at the hole will be 30 cm above the ground
level. According to the depth of the holes and theirs dimentions an
excavation technic will be choosen.The size of the hole will be choosen
depending to the pre-treatment of the soil starting from 30Х30Х30 сm and
reaching up to 60Х60Х60cm.
Key Factors:
Soil analysis for determining the content clay and microelements and
for estimate how much the soil is suitable for Paulownia growth;
Soil preparation is fundamental for the satisfactory growth;
The weeds control is the most important aspect in the preparation of
the place and the tree growth during the first and the second year;
Irrigation is necessary if the summer rain is insufficient;
1.7 Diseases and enemies
Paulownia plantations do not suffer the typical diseases for the region. A
problem could be the sensitivity of the stem of stem and root decay in a
young age. Preparations against the grey decay and others is used for avoiding
it. The fight is not hard, but the disease depends on the iggiration
manner of the planting material during the first months and the
drainage of the soil. The presence of competitive vegetation in 50 cm zone
around the root system deteriorates significally the growth in height and
diameter. The constant cleaning around the stems is real ly
important because i t can af fect considerably the yield.
1.8 Yields
According the conditions, the choosen genotype /hybride kind/, the keeping
and the rest of the factors normally affecting the traditional crops, the yields of
Paulownia could vary into serious limits from 30-40 tdm/ha/y (tons dry matter
per hectar per year) or at biennial rotation cycle to 70-80 tdm/ha.
1.9 Harvest the production
The harvest of Paulownia produc t ion happens f rom late autumn
unt i l ear ly spr ing . At normal conditions this gives a period of 3 months
from December to the beginning of March. This time troubles the machines
entry and must be considered. If the conditions suggest earlier development
the buds cutting shall be withdrawed back in time. In general this means
harvest of the production before the juices of the plant begins their
movement in the stem and that way the stored in the roots reserves to assure
the development of new ones.
There are three manners for harvesting the crops. Direct harvest like wooden
chips, harvest of entire stems and harvest of cutted sticks with certain lenth
and each of them possess its advantages and disadvantages.
In most of the cases the harvest of the production is a process of cooperation
between different owners due to the specific of the process and the price of
the engines used. The separately purchase and the use of such machine is a
right choice only in few cases. Here the necessity of drying places shall be added
as well as the requirements of the chain with providers and the final users of
the production. All of that aggregate determines the choice for harvesting and
the following activities with the production.
1.9.1 Direct collection of chips
In that case the culture will be harvested and processed in chips at the cutting
of the stems. In that case the material might need artificial drying in
order to escape decay. Most of the machines for this type harvesting are
constructed to gather double rows by one turn possessing significantly changes
picking heads, that will be installed into the standart machines for foraging. The
machine cuts the stem and turns it after into chips and throw it in a trailer. In
this case the already used trailers for collecting a silage could be applied. If the
production is harvested while it is fresh, the quality of the chips is much better
and the fuel costs and amortization of the machine will minimize. This is the
most effective operation to harvest the production but also requires special
drying places. The chips starts to rot as like composting, that leads to energy
loss. Dryiers with ventilated floors used for the cereals are successfully applied
in this operation. In addition the chips is collected and dryied after the cereal
harvest has been already dryied and by this way the expensive equipment is
used additionaly. This type harvesting machines have the capacity of 5-6
hectares per day. In the case for Bulgaria where the lands are more compact
and scattered the capacity could be esteemed as 3-4 hectares per day.
1.9.2 Harvest of whole stems
In this case the culture will be hatvested on whole stems. Multiple conditions
must be considered while choosing the harvest method.
The machines mostly chop and release the stems, that are important for
harvesting, removing and storage like a separate operations.
There are still no effective machines that could tie the chopped stems and it
might be difficult to work with 6-10m rods. The collected stems shall be
transferred for second time for slicing before they turn into use. The collected
stems are being grouped straight in a formation similar like haystack. Thus
they are going to have good enough natural air ventilation for the necessary
period of about 2 months for wood drying without decompose. In this case it
means that the special needful dryers in the direct chips collecting are
necessary. The quality of the chips obtained by this method is lower than in a
case of direct collecting. Slicing the chips is more energy intensive operation
because the chopped wood has been dried. The machines used for cutting the
stems have the capacity of 4-6 hectares per day, thought they remains at the
places of cutting and needs to be collected and transported. Even that this is
more expensive havest method in terms of operating costs in Bulgaria in the
presence of small plantations, scattered plantations and the lack of expensive
dryers and picker machines, this method might turn out more applicable and
practiced.
1.9.3 Harvest rods.
This method takes an average place between the direct collecting of chips and
the cutting of whole stems. This type picker machines has been developped for
sugar cane and forms small pieces from the whole stem of length about 5-10
сm in a way similar of the chips collecting. The machine throws the pieces in a
trailer for removal from the plantation. In this case the bigger size of the
pieces and the ameliorated air circulation between them the natural drying is
possible in a way similar to the collecting of whole stems. This pieces also
needs additional cutting before use in order to maximize the combustion
efficiency, but unlike the whole stems they could be easily manipulated. Here
again the quality of the chips is worse than the one obtained directly, because
the material that has been cutted is relatively dry.
1.10. Drying and storage
Regarding the fact that the need of fuel supplement is amost constantly
throughout the whole year and depends on the final user it will requires a
specific type drying and storage. The part of the providers chain is not enough
clarified and requires work on the problems and theirs addressees. The fresh
harvested crops are having moisture around 21.3% (for comparison another
energy crop is having natural moisture around 50%) and the need of drying is
determined by the choosen harvest method. Generally this is only the directly
collected chips that might need artificial drying. The whole cutted stems are
not abe to reheat by themselves and to provoke decay and because of that will
get dry naturally. The artificial drying is an expensive operation and requires a
precise quantity of energy for decreasing the humidity to 20% so the chips
could stay stable for a longterm and for that reason the cutting shall be
pursuant in order to escape the necessity of artificial drying.
The drying is necessary because when the humidity is increased the cellulose is
easier digested by the fungi and bacteria and the tree starts to decay. This
causes loss of calorific value and generally loss of its fuel quality. The percent of
chips drying depends on the combustion chambers. The big furnaces are
accepting 30% moisture chips when the smaller ones are working more
effectively with dry material. Completely dry material is having the energy value
of 19 MJ/kg and the one with 22% humidity is having 17MJ/kg for a reason that
part of its energy is used for the drying process.
1.11. Recovery at a place
When the Paulownia plantations reaches the end of their living cycle, the area
shall be transformed into a grass land or infield. The root system of Paulownia
is significant and its mechanical removal could cause a substantially damage
of the soil.
After the last harvest gives new sprouts, when they are at the height of 30-50
сm), Paulownia is exclusively sensitive to herbicides, so the one time use of
herbicide (5l/ha glyphosate) is enough for destructing the actively growing
culture. The culture shall be left at least two weeks after the spraying in order
to ensure the full absorption and penetration of the herbicide.
By using a cultivator from the sprouts and the soil surface layer a shallow
tillable layer appears, where a cereal will be planted.
Furthermore the bigger part of the root system is in the soil without harming its
structure. A recovery like that of the lands for growing cereals could last whole
season. The conversion of the land into a complete tillable land could last
longer time so the roots can decay. Otherwise there is going to be a need of
a much complicated and expensinve mechanical removal of the sprouts
and the roots.
2.0. ECONOMIC APPLICATION
The final bruto energy consumption in Bulgaria could be summarized into three
general groups; for heating and cooling needs (44,1%), electroenergy
consumption (30,3%) and transport energy (25,6 %). Therefor it is difficult to
understand why most of the initiatives for energy production from renewable
sources is directed to production of electricity. In addition, the technologies
for heat generating are the most developed than all the others. For that reason
there is a great interest in them and into their development as a renewable
sources for energy, that are most applicable for the agriculture in Bulgaria. The
logistics for supply of very large megawatt plant composite by multiple small
producers will represent a serious logistic problem. The supply of relatively
small central (less than 1 MW) from small cooperative is the most sustainable
development way.
In this way the possibilities for delivery of heating to the final user are increasing,
threw one company for energy deliveries, having this way the for selling product
with additional costs and not a raw material (wooden chips).
2.1. Burning, Gazification and Pyrolysis
There are three thermodynamical processes that could be used for converting
the energy from the wooden chips into a usable energy – heat or electrical;
Burning, gasification and pyrolysis. In small dimentions, as it would be practical
for the conditions in Bulgaria the technologies for direct burning already exists
and they are applied, the technologies for gasification in small dimentions are
still developing and their commercialization is just about to happen, the
pyrolysis is still in the stadium of research and development.
2.1.1. Burning
Generally this is the most effective way to obtain heat from the wooden chips.
The process includes burning of the wooden chips with a sufficient amount of
2.1.2. Gazification
This is a shape of partlial combustion where the included in the chips energy is
being released under the shape of flammable gases, water vapors and
carbon monoxide. This will be achieved by heating up the fuel up to hight
temperatures (over 700 oC) at controlled deficiency of oxygen interfering the
full combustion up to water and carbon dioxide. This is relatively simple
chemical process and could be implemented in multiple systems (updraft,
downdraft, fluidised bed) depending on the place where the oxygen is being
saled or its direction of transit in the gazificated container.
The obtained gazes are being cooled and purificated and the combustion ends
in a standart internal combustion engine. Moslty used is the compression
ignition engine (diesel) as the most tolerant to the gas with a different nature.
The small amount diesel fuel (10%) is being used for improving the gas
combustion. This is having the additional advantage, in the abscence of gas
from wood the eingine could run entirely on diesel fuel.
By the use of gas obtained of wood for fuel in the eingine it produces 75-80%
by the power than if it works entirely on diesel fuel. Small systems from the
range of 100-250KW generated electricity are being developed but non
commercialized. The adaptation of wood to gas is relatively seamless but its
purification from particles and soots in order to allow the seamless
combustion in the eingine is a serious problem.
The efficacy evidences for the energy convertion by the use of eingine and
generator shows that it is in the range of 25-30%. But if the generated extra
heat is being used for electricity generation the efficacy could be increased up
to 75-80%. The gas obtained in the process is with low calorific value between
4 and 5 MJ/m3 and it is not economically viable for storage, so it is used at the
time of its formation.
This is the technology that is still in a process of research and development. It
is including heating up of the chips to temperatures from 4300C - to 7000C
with a full lack of air, whereat an energy is being released as a pyrolytic fuel,
dense carbon and inflammable gases. The relative parts of these products
depends on the used temperatures and from the residence time of the chips in
the reactor. The main advantage in this process is that it can produce liquid
fuel that can be stored and transported relatively easy. It has calorific
equivalent of 16MJ/kg, but it is acid and has a significant water content, i.e. it
is corrosive and appears unstable.
2.2 Bioremediation
Using Paulownia as a renewable energy culture with short rotation cycles is an
economically justified investition not just because of the high energy cost at
the moment. In this context we also should add the ability to extract
compounds from the contaminated soil and water, that further increases the
stability of the investment. This process called bioremediation is especially
applicable in the contemporains climate changes, where shall be taken
actions for the management of the waste from farms and sewage.
For many reasons Paulownia is very good kind for recycling (bioremediation)
of wastes. Paulownia uses significant quantities of water compared to other
wooden species. The huge root system of Paulownia and its descenging into
depth of about 2 me t r e s , cont r ib u t e s e x t r a c t i o n o f c omp o u n d s
n o t j u s t f r om t h e t o p s o i l b u t a l s o f r om d e e p e r
h o r i s o n s . T h i s c h a r a c t e r i s t i c o f t h e t y p e r e p r e s e n t s
e x c e l l e n t s k i l l s f o r ame l i o r a t i o n o f h i g h l y c o n t ami n a t e d
s o i l s , b u t a l s o t h e a p p l i c a t i o n o f wa s t e wa t e r s f o r i t s
i r r i g a t i o n . T h e h u g e l e a v e s , t h e f a s t g r owt h , t h e t o l e r a n c e
t o p o l l u t i o n a n d t h e s i g n i f i c a n t e v a p o t r a n s p i r a t i o n
contributes the extraction of destructive compounds from the soil and
water.
Precisely these characteristics are making Paulownia and engine for sustainable
bioremediation. Guiding principle f o r a l l t h e s y s t e m s f o r
b i o r e m e d i a t i o n i s t h a t t h e s u b s t a n c e s i n c l u d e d i n
t h e s y s t e m t h r o u g h t h e c o n t a m i n a t e d s o i l a n d
w a t e r a r e b e i n g e x t r a c t e d a f t e r t h e h a r v e s t a n d
t h u s t h e s y s t e m i s s t a b l e .
In a personal research (Zhu, 1991) f i n d s o u t t h a t 8 y e a r s o l d
P a u l o w n i a a r e a b l e t o t a k e a w a y N with a speed of 930 kg/ha
per year estimated according to the average nitrogen content in the leaves of
2,6%. World Institute for Paulownia describes the type as owner of the
exceptional ability to take away nitrates, heavy metals, pollutants and other
elements from the shallow and the deep part of the soil. With the loss of the
leaves the plant enriches the soil after once it has recycled many destructive
ingredients.
3.0 ENVIRONMENTAL IMPACT OF THE USE OF PAULOWNIA
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The use of Paulownia at short rotation cycles as regards to the environment
and the biodivercity differs in several general characteristics from the crops
grown for food.
With the crops c o m m o n l y m o s t u s e d i s a s m a l l p a r t
f r o m t h e w h o l e p l a n t e v e n w h e n t h e r e a r e m i n i m a l
c o s m e t i c d a m a g e s o f t h e c r o p y i e l d s a r e
s i g n i f i c a n t l y r e d u c e d .
With Paulownia when the whole plant is in use similar cosmetic damages are
having minimal impact and the step, where significant economical losses starts
is considerably high, that leads to savings from pests combat and diseases
control.
Paulownia forms relatively stable habitat comparing to the annual crops,
althought the harvesting invades it in a way. However, if Paulownia’s blocks
are at different ages (one and two years) the natural enemies of the pests can
settle and survive in neigborhood by naturally controlling the pests. Similar
cases are observed with serious pests as leaf beattles and rust. Any change in
the use of the land from one with annual plowing and cereals in Paulownia
plantations inevitably leads towards changes in the ecology/biodivercity.
Plantations of Paulownia could also be buffers in terms of limiting the diseases
transfer between the different agricultural. A full assessment could be made
only after long use of Paulownia plantations operated at the same location
combined with the relevant scientific assessments. Theese changes will be
affected by the use of herbicides, pesticides, inorganic and organic fertil isers,
wastewaters and cyclicality of cutting. In general the overall effect at the
places where Paulownia is replacing the intensive agricultural crops
cultivation will be positive, but where it replaces improved pastures it will
have minimal effect.
3.1.Flora
The change in land use from one for pastures and annual crops to another for
multiple year tree type with regular harvest will change the ground flora. The
species divercity in the plants community under Paulownia will firstly grow very
fast and subsequently slow as the species are changing until reaching and
establishing a poorer species community. Starting point of these changes and
the rate of change depends on the soil type and the factors: treatment with
herbicides, the use of fertilisers and the crop collecting periods.
The dencity of the plants in the Paulownia p l a n t a t i o n s i s h i g h .
With other similar crops it has been found that initially there are many
germinating seeds and subsequently shortly living many years (often
aggressive trees and bushes) and at the end with perennial types with
conservational values.
Plantations established at pastures are developping richer multi flora
plantations than plantations build up on pastures with annual plowing
and treated with herbicides.
Harvesting the production prevents the creation of completely stable
ground vegetation. Instant harvesting of the biomass has a dramatical
impact over the microclimate, sunlight, use of the water resulting as
instant increase in the species composition. During the next year it will
be less again.
Herbicides – Paulownia requires the use of herbicides for its stable
establishment in the place and the cultivation at least during the first
two exploatation seasons. Subsequently the tolerance to weeds is much
higher and this increases the level for uptaking pre care for control over
the weeds. In time gradually the invasive weed species are reduced and
it is only observed less competitive multi year shadow resistant
vegetation.
3.2. Invertebrates
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The richness of insects with Paulownia is considerably less than with other
fast growing species. There are also some leaves flies and aphids.
This causes an decrease in the necessity for insecticides use.
Species with conservational importance are not observed with
Paulownia.
Research on the condition of the earth worms under Paulownia
plantations has not been made. During research on other fast growing
cultures has been observed their decrease. In multi year established
willow plantations in Germany they are showing an increase.
The divercity of invertebrates at the ground floor is mostly according to
the nature of the ground vegetation. Intensivly cultivated plantations are
unlikely to provide rich habitats.
After cutting the biomass a short term peaks could be expected in the
number and the divercity of the invertebrates.
The invertebrate fauna is considerably poorer than the fauna found at
the annual crops despite the significantly greater divercity of the conditions
for existence.
