Abstract:
The
aim of this investigation is to find out the feasibility of anaerobic digestion
process for dairy cattle and swine manure in
Key words: anaerobic
digestion, biogas, co-digestion, energy policy, renewable energy.
1.
INTRODUCTION
Poverty, malnutrition,
violence, overpopulation and drug trafficking, are several problems affecting
the world. These terms are heard every day in the news, but overall the main
issues nowadays are “increase of oil prices” and “energy scarcity”.
New ways to produce energy,
which does not negatively affect the earth, should be found. A solution in long
term which ensures world sustainability is needed. Renewable energies could be
the solution for these problems, if they are applied with the right technical
and ethical way.
Energy can be produced by means
of anaerobic digestion of organic matter in absence of oxygen, to produce
biogas; a mixture of methane and carbon dioxide. This biogas can be transformed
into electrical and thermal energy by means of an engine.
2.
METHODOLOGY
The first phase of the study will be based in the
understanding of the general framework of the countries. The next phase will be
to continue with the investigation of the biomass potential, which could be
digested in a biogas plant, from this, will be calculated the energy potential.
In the third phase, several economical feasibility cases will be analyzed, with
the same amount of substrates and energy yields. In order to understand the
influence of the different energy policies, in each country. At the end, some
recommendations will be suggested.
3.
RESULTS
3.1 Country framework.
3.1.1 Country economy.
In
order to analyze the feasible potential of the two countries, the general
framework should be recognized.
|
Country |
|
|
|
Official Language |
Spanish |
Italian |
|
EU accession |
January, 1986 |
March, 1957 |
|
Area |
504.030 km2 |
301.318 km2 |
|
Population (2007) |
45.200.737 |
59.619.290 |
|
Density |
90 people/km2 |
197.6 people/km2 |
|
GDP(Nominal, 2007) |
908 € trillion |
1.304,3 € trillion |
|
GDP per capita |
19.858,0 € |
22.328,6 € |
|
Currency |
Euro |
Euro |
Table 1. General country
data. [1-2]
Spain: Spain has a strong
economy, it is the fifth largest in Europe (and eight worldwide) with strong
sectors in real estate at 16% GDP, tourism at 5% GDP, and agriculture,
livestock and fishing at 2,9% GDP. Livestock activities represent 40% of the
final agrarian production, with a high swine production (the second largest of
3.1.2 Biogas background and present situation.
Biogas production in
In
2007 has been estimated a capacity of 158 MW in
Figure 1.
3.1.3 Farmer traditions.
One
of the most important issues, at the moment of planning the implementation of a
biogas plant is to understand, the livestock traditions and farmers techniques,
to evaluate if biogas plants are suitable for them. The most important
parameters are the housing and manure recollection. There are two main housing
systems: extensive farming is when
the animals live in big extensions of land, outside stables and intensive housing, is the accommodation
of animals inside stables. Intensive housing is a requirement for farms which
want to construct a biogas plant, due to the recollection of manure is possible.
In order to recognize the
farming practices, a small survey was done to farmers. The aim of the interview
was to identify the common practices done by the farmers.
|
QUESTION |
Swine
Farming |
Dairy
Cattle Farming |
|
Average
animals / farm |
3.000-12.000 pigs/farm. |
Average 70-100 cows/farm. A big farm will have
300-500 cows/farm |
|
Type of Housing |
99,9% Inside stables |
Inside stables. Only cows with low milk production
are outside. |
|
Type of bed |
They are not using straw. |
Use of wood residues, sawdust, or sand. Not straw
(expensive). |
|
Manure recollection |
Almost all farmers use "slotted floor”. |
Almost all farmers use "scraper" system. |
|
Manure use after
recollection |
Used as fertilizer or it is transported to a third
person. |
It is used as fertilizer. Some of them apply
separation systems. |
|
QUESTION |
Swine
Farming |
Dairy
Cattle Farming |
|
Average
animals / farm |
Average 650 animals / farm. A big farm will have
5.000 heads. |
Average 10-500 animals /farm. Depend on the
location. |
|
Type of Housing |
Almost all the farms practice intensive stables. |
Most of the farms use intensive housing with
stables. |
|
Type of bed |
Straw, sawdust or shaving wood. |
Straw, others use rubber carpet, sand or sawdust. |
|
Manure recollection |
Slotted floor. |
Almost all use scraper. |
|
Manure use after recollection |
Manure is applied on land as fertilizer; other farms
are starting to use manure to produce energy (biogas). |
It is used as fertilizer (some make separation)
others move or sell the manure, or use it for biogas. |
From the previous
survey can be concluded, that both Spanish and Italian
structure farms are suitable for install biogas plants.
3.1.4 Energy policies.
Figure 2. Comparison between fixed tariff and
bonus incentive, in
Figure 3. Comparison between fixed tariff and CV incentive, at Italian
policies. [20, 22].
3.2
Energy Potential.
3.2.1 Animal inventory statistics and estimation in 2008.
At
this part of the study will be calculated; the energy potential from biogas
plants, supplied by swine and dairy cattle manure.
In
order to estimate the amount of manure produced by the animals, census
statistics have been studied to estimate the amount of animals in 2008.
Figure
4. Number of animals (swine and dairy cattle), in thousands for
From
this graph and with the tendencies lines, was estimated the amount of animals
for both countries, in 2008:
3.2.2 Availability of co-substrates.
Spanish
communities with more surfaces dedicated to agriculture are: Andalucía, Aragón,
Castilla y León, Castilla-La Mancha and Extremadura, they cover 78% of all
The regions most utilized
for agriculture are: Piemonte, Lombardia, Trentino-Alto Adige, Veneto,
Emilia-Romagna, Toscana, Puglia, Sicilia and Sardegna
3.2.3 Potential animal manure production.
In order to calculate the
amount of energy that can be produced from animal manure, should be studied the
amount of manure produced per animal.
In average pigs and dairy cattle produce:
|
Animal |
Manure production |
Unit |
|
Swine |
6,5 |
kg/animal-day |
|
Dairy cattle |
45 |
kg/animal-day |
Table 1. Average manure production. [29-31]
Swine Manure Production:
|
Item |
Unit |
|
|
|
Animal estimated
census 2008 |
Units |
26.926.000 |
9.300.000 |
|
Manure
production |
ton/ animal-year |
2,37 |
2,37 |
|
Total manure
production |
ton/year |
63.881.935 |
22.064.250 |
Table 2. Estimation of the swine manure generated per country.
Dairy Cattle Manure
Production:
|
Item |
Unit |
|
|
|
Animal estimated
census 2008 |
Units |
984.000 |
1.903.000 |
|
Manure
production |
ton/animal-year |
16,43 |
16,43 |
|
Total manure
production |
ton/year |
16.162.200 |
31.256.775 |
Table 3. Estimation of the cattle manure generated per country.
3.2.4 Manure Energy Potential.
After estimate the amount of manure produced from the animals, the following
parameters to analyze are the composition of the manure, which will determine
the amount of biogas to be produced (potential energy per ton). Manure
composition will vary depending on several factors as: type of installation, quality and quantity
of food and water, livestock practices, dilution of waste water and rain water,
cleaning systems, etc.(See annexes)
Estimations
realized with typical manure compositions and energy yields (see annexes),
achieve the following results:
§
Swine manure: 39,31kWh/ton manure
§
Cattle manure: 32,34kWh/ton
manure
|
Parameter |
Unit |
|
|
||
|
Pig
manure |
Cattle
manure |
Pig
manure |
Cattle
manure |
||
|
Substrate input |
million ton/year |
63,88 |
16,16 |
22,06 |
31,25 |
|
Energy Potential |
MW |
314 |
65 |
108 |
126 |
|
Total Energy Potential |
MW |
379 |
235 |
||
Table 4. Potential energy capacity from swine
and cattle manure, for
Table
4, illustrates the amount of energy that could be obtained from swine and
cattle manure, for both countries. In the case of
On
other side, Italian swine and cattle manure could produce an estimated 235 MW.
Comparing with the current 194 MW installed in 2007; the potential energy could
duplicate the actual capacity. In this case, 54% of the potential energy
capacity comes from the dairy cattle farming and the other 46% from swine
farming.
3.3 Financial Framework.
3.3.1
Transport
cost.
Substrate transport cost will
influence dramatically the cash flow results in a biogas plant design. Therefore, the biogas plant has to be installed as near as possible from
the substrates.
Transport
costs, depends on several factors as:
- Fixed costs: truck depreciation, taxes, licensing fees, insurances, etc.
- Variable costs: distance traveled, employer costs, maintenance,
additional labor, etc.
Several
studies have been revised, in order to determine an average price of manure
transport. Even if the costs will decrease with the increase of distance, an
average price can be established as: 0,097€/km-ton for 2008. [32-35].
3.3.2
Economical Analyzes.
For both countries was analyzed the financial estimations
with the fixed tariffs, if electricity is sell to the grid.
Recommendations:
§
The current study describes
an energy potential. It is recommended to investigate the available energy, as
a consequence of the technical limits. For example no possible access to the
manure due to low density of animals per farm, limitation of connection to the
grid, farms with extensive housing, etc.
§
It is suggested to
investigate the procedures and authorization processes, required to obtain the
permission for the biogas installations in each country.
§ Biogas companies should develop smaller systems, for example offer 150kW
plants to farmers with low concentration of animals.
4. CONCLUSION
Spanish and
Italian structure farms are appropriate for the construction of biogas
installations. Mainly due to the manure recollection systems; use of slotted
floor at swine farms and scraper at cattle farms.
With
the amount of manure produced by the animals (pigs and dairy cattle) in each
country, was estimated a total energy potential. Was calculated 379MW in
Even
if there is enough manure in both countries to install biogas facilities, is
required the use of co-substrates or energy crops, due to the low total solids content
in manure.
Biogas
installations at
