Written By: Stanley Ebikonbowei Tambou
It may interest to know that the world is gradually shifting from consumption of fossil fuel energy which is not environmentally friendly, renewable and sustainable to a more reliable energy commonly called bioenergy.
Traditional fossil fuel such as coal, crude oil and natural gas which is one of major sources of energy for cooking, lighting, electricity, transportation and heating has done more harm than good. In the sense that, it causes indoor and outdoor pollution as it emits objectionable gases including ammonia, carbon monoxide, carbon (iv) oxide and hydrogen sulphides and degrade land, air and water quality which consequently impact the health of man, aquatic and animal life.
Therefore, by the implication of the above, researchers discovered a new technology, now widely advocated in developing countries to redeem our fragile environment from climate change and global warming through anthropogenic activities and overdependence on fossil energy to a eco-friendly energy called biotechnology or biogas technology.
FROM WASTE TO ENERGY
Biogas technology converts waste to energy especially organic fraction of municipal solid waste (OFMSW). Municipal solid wastes are waste generally group into three broad categories:
ii. Industrial waste and
iii. Agricultural waste
Waste is anything material otherwise thrown away after the complete utilization. Technically, one man’s wastes can become another man’s treasure as a consequence of technology and educational disposition.
Nowadays, waste whether organic (biodegradable) and metal, glass materials (non biodegradable) has be forge into useful material. Thus, the 4Rs of waste management, reduce, reuse, recycle and recovery.
Waste processing, therefore, is to convert uselessness to usefulness. In other words, WTE technology utilizes wastes as feeds, food, feedstock, fertilizer, fuel and finance.
Waste processing is the mediator of input (feeds) and output (products). It is transforming raw material useful products. Waste can be collected, processed and reuse. Hence, can be achieved through waste management techniques.
*TYPE OF WASTE TO ENERGY TECHNOLOGY
There are several WTE technology which are grouped according to development and chronology.
v. Anaerobic digestion.
THERMAL AND NON THERMAL WTE TECHNOLOGY
The above WTE techniques can be categorized into two main categories which are thermal and non thermal.
Thermal waste processing involves complete burning in the presence or limited air. Examples include, incineration, pyrolysis and gasification.
Non thermal waste processing refers to a gradual fermentation of waste materials to form compost or biogas in the presence of oxygen and absence of oxygen. Examples are composting (required oxygen) and anaerobic digestion(no Oxygen).
Although, both technology produces three products biogas, biochar and bio-liquid(leachate) yet the existence or emission of impure gases which are toxic to the environment are inevitable if not we’ll controlled. However, the best WTE technology is the anaerobic digestion which digests waste in closed and controlled container in the absence of oxygen to yield biogas under certain variables or parameters.
PARAMETERS OF WTE ANAEROBIC DIGESTION
i. Temperature: includes psychophilic 0-15°C – 15°C, mesophilic, 15°C – 25°C and thermophilic , 25°C – 70°C.
ii. pH: 6-7 range. If acidic or Alkaline inhibits methanogenesis. To maintain the pH NaOH or lime among others are added.
iii. Moisture: it must be wet and little water increases the moisture or wettability.
iv. Carbon-nitrogen ratio: More carbon tends to CO2 and more Nitrogen leads to NH3 formation respectively. Therefore, C:N ratio considerable equal.
v. Organic loading: Mass of faece used as feeds must be in the right proportion in order to get the biogas.
vi. Retention time: gas is not produced immediately the feed is fed to the digester. It has to stay or detain or retain for 21 – 30 days.
Vii: microbial populace: includes psychophile, mesophile and thermophile
STAGES ANAEROBIC PROCESS
i. Hydrolysis: reaction of water which converts organic polymers to monomers. That is, convertion of carbohydrates, fat and oil, protein to glucose, fatty acids. It is a slow process called the rate determining step.
ii. Acidogenesis: convert products of hydrolysis to acids.
iii. Acetogenesis: converts products of acidogenesis to acetic acids. It determines the methanogenesis process.
iv. Methanogenesis: converts products of acetogenesis to methane – the cooking gas. This final process of anaerobic digestion.
TYPES OF DIGESTER AND DESIGN
We have batch and continuous digester. The former is a container loaded with feeds and then sealed for days. The later is a container continuously loaded and interconnected to more containers.
Both digester size varies depending of the cost of the project.
Design construction consist of container, gas collector and connections etcetera.
FEEDSTOCK OF ANAEROBIC TECHNOLOGY
- Human faece
- Cow Dung
- Pig dung
- Chicken dung
- Fruit waste
There are collectively called biomass. That’s waste organic products.
PRODUCTS OF ANAEROBIC TECHNOLOGY/WTE
- Methane 50% (Useful)
- CO2. 20%
- NH3. Fraction
- H2O. Fraction
- H2S. Fraction
- Biosolids (useful)
APPLICATION OF METHANE
- Methane is used for cooking gas.
- It is used in gas generator for electricity.
- it used for gas engine for transportation.
- It is used for lighting and heating.
APPLICATION OF BISOLID
This is the solid waste or sludge products.
- It is used as fertilizer.
- It is used for landfilling.
Conclusively, biogas is renewable natural gas to substitute natural gas from fossil fuel that reduce air quality and causes pollution and climate change. Biotechnology can also reduce smoke generated from woodfuel and it application can help rural and urban residents with affordable gas which they can produce themselves without reliance on the government all the time for power.
Therefore, individuals, non governmental and government agencies should advocate for this innovation to safeguard our fragile environment.
Words and ideas expressed are solely by the writer@Tambou Bribeine Stanley