Abstract | Poljoprivreda posjeduje veliki potencijal u obliku poljoprivredne biomase iz koje je moguće
proizvoditi toplinsku, električnu i mehaničku energiju ili ju prerađivati u komercijalno
pogodnije oblike energije, odnosno proizvesti kruta, tekuća i plinovita goriva.
Dostupni poljoprivredni ostaci u Međimurskoj županiji su ostaci iz ratarske proizvodnje,
uključujući slamu od pšenice i ječma, stabljike kukuruza i uljane repice, zatim ostaci od
rezidbe voćnjaka i ostaci rezidbe vinograda te stajski gnoj goveda, svinja i tovnih pilića.
Budući da danas većina poljoprivrednih ostataka na području županije ostaje neiskorištena,
cilj rada je utvrditi potencijal, model prikupljanja i energetskog iskorištenja poljoprivrednih
ostataka.
Na temelju prikupljenih podataka o poljoprivrednim kulturama i poljoprivrednim površinama,
prinosu poljoprivrednih kultura, odnosu zrna i mase, donje ogrjevne vrijednosti te mase gnoja
i pripadajućeg potencijala bioplina po uvjetnom grlu izračunata je količina ostataka i
pripadajući energetski potencijal. Usporedba i valorizacija potencijalnih društvenih koristi i
troškova uspostave sustava opskrbe i korištenja poljoprivrednih ostataka napravljena je
multikriterijskom analizom. Za analizu cjelokupnog utjecaja odabranog modela na
gospodarstvo, ekosustav i ljudsko zdravlje primijenjena je metoda ekspertne procjene. Kod
odabira optimalnog prijevoznog sredstva za transport poljoprivrednih ostataka korištena je
metoda višekriterijske analize.
Rezultati istraživanja pokazuju da na području županije postoji potencijal poljoprivredne
biomase za pretvorbu u energiju, ali do sada nije bilo ulaganja u ovom području. Na području
Međimurske županije količine poljoprivredne biomase koje je moguće prerađivati iznose
323.912 t/god. Rezultati pokazuju da ukupni energetski potencijal poljoprivrednih ostataka
iznosi 1.092 TJ. Analizirajući raspoložive količine poljoprivrednih ostataka na godišnjoj razini,
udaljenost i položaj proizvodnih površina, odnosno blizinu proizvodnog mjesta poljoprivredne
biomase do centralnog postrojenja te prometnu povezanost i postojeću infrastrukturu
predlaže se proizvodnja bioplina i korištenje postojećih plinskih mreža za biometan,
proizvodnja peleta, proizvodnja biogoriva druge generacije, odnosno uspostava sabirnologističkog
centra za poljoprivrednu biomasu.
Ulaganja u pretvorbu poljoprivrednih ostataka u energiju mogu biti značajan doprinos
održivom razvoju županije. Županija treba koristiti svoje obnovljive izvore energije, a
poljoprivredni ostaci mogu biti vrlo dobar izbor, jer su održivi, okolišno prihvatljivi i poznati,
redovito dostupni i obnovljivi izvor energije županije. |
Abstract (english) | All types of biodegradable residues are desirable raw materials in the production of all forms
of useful energy. The occurrence of both increasingly stringent environmental regulations in
the last ten years and restrictions in the disposal of biodegradable residues, as well as the
limitation of breeding of raw materials, for the production of biofuels, has led to the fact that in
the foreground come raw materials that are being laid down as residues or waste. Agriculture
has a great potential as agricultural biomass, which can be used to produce thermal energy,
mechanical energy and electricity, as well as derivatives from which useful energy is
obtained. The inclusion of organic residues from agricultural production is of a great
importance, not only from the aspect biomass usage in energy production but also from the
aspect of their disposal, with direct gain through production and use of thermal energy.
Environmental problems and deficit of fossil fuels call for the need to pay greater attention in
finding procedures for preparing and using residues from agricultural production as a source
of energy. Sustainable management of biodegradable agricultural residues represents a
great challenge, as such residue is an easily accessible and usable material. Both the
advantage and complexity of using agricultural residues for energy purposes lie in the fact
that different forms of useful energy, from the same raw material, can be obtained, but the
most desirable form will depend on the purpose function of energy policy. The choice of
technology for energy management of different types of agricultural residues represents the
basis of any analysis that depends on dominant agricultural crops, agricultural production
technology and quantities of residues left over for disposal. There are three main ways to use
energy from the biodegradable part: producing a solid, a liquid and a gaseous form of a
particular biofuel. Biogas production by anaerobic digestion of organic residue is
economically a very cost-effective solution. Anaerobic decomposition is considered to be an
environmentally friendly technology, with least costs in rural areas.
Since today the majority of agricultural residues, in the Međimurje County area remains
unused, the aim of the work is to determine the potential and model of collection and energy
utilization of agricultural residues. In the broader sense, through the methodological
procedures and results described in this paper, it wishes to gain widespread knowledge on
the principles and models of managing biodegradable residues from agricultural production.
Based on analysis findings on types and quantities of biodegradable residues, along with the
determination of energy potential, analysis of collection of residues and technological
solution of energy conversion of residues, as well as on conclusions from a concrete model
of biodegradable waste management, a general, wider applicable model of management of
biodegradable residues from agricultural production will be suggested, primarily in Croatia.
The chapter „An Overview of Current Researches“ focuses on the preparation and collection
of agricultural residues, their transportation and storage and the possibilities of biomass
exploiting. One of the most important barriers in the increased use of biomass for energy
supplying is the cost of the chain of biomass supply and of technology of biomass conversion
into a useful form of energy. The period when an individual type of biomass is available is
very limited and determined by sowing, harvesting or yielding periods, weather conditions
and the need for new sowing on agricultural land. Since most biomass energy is now limited
to one-time use, large amounts of biomass for a significant period of time need to be stored,
in order to be available throughout the year to operate the plant. Local use of resources from
agriculture is the best. Such resources are too expensive to be collected and transported, but
are still economically attractive. Some residues propertie, such as heterogeneity, low volume
mass, humidity and composition variability condition collection, transportation and storage
procedures. Due to typical location of biomass sources (agricultural areas, agricultural
farms), road transportation is the most common transport infrastructure, as the only possible
way of collection and transportation of biomass. Other factors, favoring the use of road
transportation, comprehend relatively short distances, over which the material is transported,
and greater flexibility the road network can offer, compared to other ways of transportation.
Biomass storage is particularly important, both for relevant investment costs in some of the
technologies, as well as for the biomass itself, energy losses and security issues, related to
the choice of storage system. Biomass can be storaged in two ways, either in an open
space, on a hard and graded surface, or in a covered warehouse. Available biomass can be
used for converting into electricity and/or internal energy (heat), by utilizing various
technologies, or it can be transformed into commercially more suitable forms of energy
(pellets, briquettes, wood chips). A part of biomass can be used to produce secondgeneration
biofuels. Within the process of organic biomass treatment, the problem of bad
smell can be solved, as well as reduce volume, obtain nutrients, reduce polution potential
and get energy from waste.
The chapter „Materials and Methods of Work“ contains description of the research area,
biomass potential assessment and description of the analysis, used in the research. Based
on collected data on agricultural crops and agricultural areas, yield of agricultural crops, grain
and mass ratio, the lower fuel value and mass of manure and the corresponding Nm3 biogas
per conditional throat, the amount of residues and associated energy potential was
calculated. Comparison of different models as well as valorisation of potential social benefits
and costs of establishing a system of supply and utilization of agricultural residues was made
by a multicriteria analysis. The method of expert assessment has been applied to analyse
the overall impact of the selected model on the economy, ecosystem and human health.
The chapter „Results and Research Discussions“ contains the results of potential availability
of residues of the most abundant agricultural crops, both with the availability of livestock
residues in the County of Međimurje, the model of collection of agricultural residues and the
estimation of immeasurable costs and benefits of utilisation of available agricultural residues.
Accessible residues in the Međimurje County are those from the production of crop, including
wheat and barley straw, corn and rapeseed stalks, as well as residues from apple plantation
and vineyard pruning and stall manure of cattle, pigs and fattening chickens. In the period
from January to April, fruit trees and grape vine pruning residues are available in the county.
Later, partly at the end of June and mostly in July, residues from wheat, barley and rapeseed
harvesting are available. During September, October and November, residues of corn
harvest is available and residues of fruit trees pruning is available in November and
December. Residues from cattle production are available all year round, and depend only on
the duration of animal fattening. The research results show that there is potential to convert
agricultural biomass into energy in the County, but there have been no investments in this
area so far. In Međimurje County, the total amount of agricultural biomass represents
323.912 t/year, so that 42.680 t/year of residues come from crop production and production
of fruit and vineyard and 281.233 t/year of residues come from livestock production. Based
on these 30% of quantity, the energy value of the amount of 1,092 TJ can be obtained. The
energy potential of crop and fruit and vineyard production represents 707 TJ, and that of
livestock production represents 385 TJ. The energy potential is concentrated in the south of
the county, exactly in the area of Čakovec and Prelog towns and municipalities of Nedelišće
and Mala Subotica. Total value of the energy potential of the amount of 1.092 TJ/year, in the
county area, represent 21% of potential of immediate consumption of energy in the
Međimurje County of the amount of 5.128 TJ/year. Biomass is best to store in a closed
warehouse, and under controlled conditions, underlining the fact that the most expensive is
are the investment costs, but it also offers greater opportunities for long-term storage of
residues, which is particularly important with regard to the seasonal availability of plant
residues in the county. By applying a model of concentric circles in Međimurje County, the
first filling will be made from the 1st collection unit, namely from the temporary storage space,
located at a distance of approximately 30 km from the central location. Then, filling from 8
collection units, which are located at a distance of approximately 15 km from the central
location will be made and, finally, from filling from 6 collection units, located at a distance of
approximately 5 km from the central location will be made. A semi-trailer tractor, to all
established criteria, is proven to be the best choice, both in terms of ability, namely ability to
receive agricultural mass, as well as in terms of efficiency and overall cost of transporting
agricultural residues. By analysing the available quantities of agricultural residues, on annual
basis, the distance and the emplacement of production areas, namely the proximity of the
production site of agricultural biomass to central plant, as well as the traffic connection and
existing infrastructure, production of biogas, both with utilisation of existing gas networks for
biomethane is suggested, along with production of pellets, production of second generation
biofuels, namely establishment of a collection-logistic centre for agricultural biomass.
Based on the researches conducted, it can be concluded that there is potential for energy
conversion of agricultural biomass in the area of Međimurje County, and that only 30% of
plant residues can satisfy a part of estimated needs of energy consumption of the county.
Investments in converting agricultural residues into energy can make a significant
contribution to the sustainable development of the county. Investments in the field of
agricultural residues conversion into energy can be a significant contribution to the
sustainable development of the County. Međimurje County needs to utilise its renewable
energy sources, and agricultural residues can be a very good choice for it, as they are viable,
environmentally acceptable and well-known, regularly accessible and represent a renewable
energy source for the County. |