1. WASTE DISPOSAL AND ZERO WASTE
Waste is incinerated to convert it into thermal energy. Waste is also disposed of by burying (landfilling). Only organic waste is decomposed to produce methane gas. All solid materials inside (paper, plastic, etc.) remain underground for many years. With the pyrolysis system, which is the main subject of our project, waste is converted into solid, liquid, and gas forms. Each of these products is utilized separately.
1.1 - What is Pyrolysis?
Pyrolysis is one of the thermochemical processes. Pyrolysis occurs when plants are exposed to hot, oxygen-free environments. The formation of energy sources such as petroleum, coal, natural gas, and charcoal is actually a type of pyrolysis.
Pyrolysis is a term derived from the Greek words "pyro" meaning heat and "lyse" meaning to break apart; it refers to a thermochemical process in which organic materials undergo thermal decomposition at high temperatures in an oxygen-free environment. At the end of the process, the fixed carbon and volatile matter within the organic materials are separated. By condensing the volatiles, two different fuels are obtained in liquid and gas forms. In simple terms, pyrolysis is the breakdown of large molecules into smaller gas, liquid, and solid molecules.
1.2 - Pyrolysis Process and Types
During the pyrolysis process, the chemical bonds of biomass exposed to pyrolysis are thermally decomposed in an oxygen-free and high-temperature environment. Large hydrocarbon molecules are broken down or rearranged into simpler molecules. In general, the temperature ranges between 400–600 °C and the pressure is atmospheric.
Pyrolysis yields solid, liquid, and gas products. The type and amount of products depend on factors such as the type of biomass, heating rate, and final temperature. According to the time and temperature parameters applied during the process, pyrolysis is divided into five main groups: slow, mild, medium, fast, and flash pyrolysis.
1.3 - Usage Areas and Economic Contributions of Pyrolysis Products
The most well-known pyrolysis process is the production of charcoal (biochar) through slow pyrolysis. Also known as degasification, the target product is the solid output. Generally, wood piles are stacked and covered with soil, and carbonization of the wood pieces is achieved by burning in a limited air environment. The gases released during charcoal production are emitted into the atmosphere. However, if condensed and collected, a liquid product consisting of a mixture of organic chemicals with a lower average molecular weight than wood and water is obtained. In addition, non-condensable gas products are formed, including CO₂, CH₄, CO, H₂, and N₂.
For example, wood waste is shredded down to 3–5 mm. Then, once the pyrolysis system is heated up to 400 °C, waste feed begins. If the residence time in the system is 15–30 minutes, the result is 30% solid (biochar), 30% liquid (bio-oil), and 30% non-condensable gas. If the residence time is 10–20 minutes, the result is 15% solid, 70% liquid, and 15% gas. In conclusion, except for iron and glass, all waste is separated by pyrolysis based on temperature and time into solid, liquid, and various gas phases for recovery. Our pyrolysis R&D will be shaped within this framework.
In particular, charcoal production from oak trees is quite common and is mostly done with traditional methods in Turkey. For this, wood is neatly stacked into cone-shaped piles and covered with soil, then carbonized through partial burning. The oil produced from pyrolysis is used as fuel in the glass, tire, and cement industries. Additionally, it is converted into electricity using engines and generators operating with heavy fuel oil. The non-condensable gases (CH₄, H₂, CO, CO₂) are used as heating fuel in the pyrolysis system. Furthermore, excess gas is used to generate electricity.
1.4 - Agricultural and Livestock Contributions of Pyrolysis Product (Biochar)
AGRICULTURE: When biochar is applied to plants along with fertilizer, its water retention feature comes into play. Therefore, plants that normally require daily watering may only need watering once a week thanks to fertilization with biochar. Since plants absorb water gradually, they will grow more healthily and yield will increase by 25%.
LIVESTOCK: When biochar produced from oak and beech wood is added to animal feed and silage, it absorbs gases in the animals' stomachs and provides relief. Meat and milk yield increase by 25–30%. When added to cat and dog food, it eliminates fecal odor. It is a must-use product for household pets.
1.5 - Use of Pyrolysis Product (Biochar) in Treating Wastewater and Odorous Areas
Due to its high gas absorption capacity, it is advantageous to use in areas with bad odors or smoke. The porosity and surface functional groups of biochar make it a suitable adsorbent for removing heavy metals and phenolic compounds in soil and water. Heavy metals and organic pollutants in water harm human health, pollute the environment, and negatively affect the living conditions of aquatic organisms. These pollutants, mostly originating from human activities, can be eliminated using biochar.
Solution Project for the Feasible Operation of Energy Production from Natural Gas and Sludge Drying Plants within İSKİ
As SPD Waste Management Ltd., we carry out the production of pyrolysis, energy generation, and ORC systems, and undertake the design and installation of energy generation plants.
In the pyrolysis system, 90% dried sludge is thermochemically heated at 500 °C for 10–20 minutes to produce:
35–40% pyrolytic oil,
20–25% CH₄, H₂, CO, CO₂ gases,
and 35–40% biochar (organic charcoal), which is highly valuable for agriculture.
The pyrolytic oil produced is converted into electrical energy.
The gas produced is used both as fuel to operate the system and for additional energy generation.
The biochar produced can be used in agriculture, livestock, or as fuel if pelletized.
As oil and gas are removed from the biochar, pores are formed, which help retain water and fertilizer. In animals, it absorbs gases in the stomach, providing comfort and reducing greenhouse gas emissions from digestion.
Biochar (organic charcoal) can retain water up to 6 times its own weight.
Instead of watering daily, plants can be watered once a week. This results in millions of tons of water and millions of kWh of energy savings.
Cost and Return Analysis of a 5 Tons/Hour Capacity Pyrolysis Plant Using 90% Dried Sludge
5 tons/hour * 24 = 120 tons/day
Annually: 365 * 120 = 43,800 tons/year
For 40% Pyrolytic Oil:
43,800 * 40% = 17,520 tons/year
17,520 tons/year pyrolytic oil = 58,400 MWe
58,400 * 70 = 4,088,000 $/year
The gas produced is used for heating the facility.
For 35% Biochar (Organic Charcoal):
43,800 * 35% = 15,330 tons/year biochar
15,330 * 5000 TL/ton = 76,650,000 TL = 2,254,000 $
Estimated Costs:
2,254,000 $ is planned to cover personnel and maintenance expenses.
Natural gas costs for oil engines and combustion will be met by the produced gas products, so these consumption costs are disregarded.
Revenue (Annual): 4,000,000 $
Plant Cost: 11,000,000 $
11,000,000 / 4,000,000 = The plant is expected to pay for itself in 2 years and 7 months.
spd Marka tescil belgesi 2020-OE-513187PDF_250109_223442 (1).pdf
