Anaerobic Digestion of Animal Manure

Animal manure is a valuable source of nutrients and renewable energy. However, most of the manure is collected in lagoons or left to decompose in the open which pose a significant environmental hazard. The air pollutants emitted from manure include methane, nitrous oxide, ammonia, hydrogen sulfide, volatile organic compounds and particulate matter, which can cause serious environmental concerns and health problems. In the past, livestock waste was recovered and sold as a fertilizer or simply spread onto agricultural land. The introduction of tighter environmental controls on odour and water pollution means that some form of waste management is necessary, which provides further incentives for biomass-to-energy conversion.

Anaerobic digestion is a unique treatment solution for animal manure as it can  deliver  positive  benefits  related  to  multiple  issues,  including  renewable  energy,  water pollution, and air emissions. Anaerobic digestion of animal manure is gaining popularity as a means to protect the environment and to recycle materials efficiently into the farming systems. Waste-to-Energy (WTE) plants, based on anaerobic digestion of cow manure, are highly efficient in harnessing the untapped renewable energy potential of organic waste by converting the biodegradable fraction of the waste into high calorific gases.

The establishment of anaerobic digestion systems for livestock manure stabilization and energy production has accelerated substantially in the past several years. There are thousands of digesters operating at commercial livestock facilities in Europe, United States,  Asia and elsewhere. which are generating clean energy and fuel. Many of the projects that generate electricity also capture waste heat for various in-house requirements.

Important Factors

The main factors that influence biogas production from livestock manure are pH and temperature of the feedstock. It is well established that a biogas plant works optimally at neutral pH level and mesophilic temperature of around 35o C. Carbon-nitrogen ratio of the feed material is also an important factor and should be in the range of 20:1 to 30:1. Animal manure has a carbon – nitrogen ratio of 25:1 and is considered ideal for maximum gas production. Solid concentration in the feed material is also crucial to ensure sufficient gas production, as well as easy mixing and handling. Hydraulic retention time (HRT) is the most important factor in determining the volume of the digester which in turn determines the cost of the plant; the larger the retention period, higher the construction cost.

Process Description

The fresh animal manure is stored in a collection tank before its processing to the homogenization tank which is equipped with a mixer to facilitate homogenization of the waste stream. The uniformly mixed waste is passed through a macerator to obtain uniform particle size of 5-10 mm and pumped into suitable-capacity anaerobic digesters where stabilization of organic waste takes place.

In anaerobic digestion, organic material is converted to biogas by a series of bacteria groups into methane and carbon dioxide. The majority of commercially operating digesters are plug flow and complete-mix reactors operating at mesophilic temperatures. The type of digester used varies with the consistency and solids content of the feedstock, with capital investment factors and with the primary purpose of digestion.

Biogas contain significant amount of hydrogen sulfide (H2S) gas which needs to be stripped off due to its highly corrosive nature. The removal of H2S takes place in a biological desulphurization unit in which a limited quantity of air is added to biogas in the presence of specialized aerobic bacteria which oxidizes H2S into elemental sulfur. Biogas can be used as domestic cooking, industrial heating, combined heat and power (CHP) generation as well as a vehicle fuel. The digested substrate is passed through screw presses for dewatering and then subjected to solar drying and conditioning to give high-quality organic fertilizer.

Zero Waste Trends to Watch

Most people have heard about concepts such as single-stream recycling, but there’s another approach known as zero waste. People who support the concept of zero waste agree that, in a broader sense, it means reducing dependence on landfills and increasing reliance on material recovery facilities. But, after that, the definition varies primarily based on industries, manufacturers and even entire countries.

Even so, there are inspiring trends that show how people and companies are working hard to reduce the amount of waste produced, thereby getting ever closer to that desirable zero benchmark. Below are some of the major trends taking place across the world in the field of zero waste:

More Reusable Packaging

We live in a world where it’s possible to order almost anything online and have it quickly arrive on a doorstep — sometimes the same day a person placed the order. And, society loves the convenience, but the dependence on delivered products causes an increase in packaging materials.

It is often astounding how many packing peanuts, layers of bubble wrap and cardboard cartons come with the things we buy. And, the manufacturers and shipping companies consistently bring up how boxes get dropped or otherwise mishandled during transit, making the extraordinary amounts of protective packaging products necessary.

On a positive note, a company called Limeloop makes a shipping envelope designed from recycled billboard wrapping people can reuse thousands of times. Another company called Returnity communicates with distributors to urge them to use the establishment’s boxes and envelopes, both of which people can rely on dozens of times instead of throwing them away after single uses.

If you are a business looking to adopt eco-friendly practices, you should read this article on green packaging methods.

Ceramic Mugs in British Coffee Shops

In some regions of the world, customers who visit coffee shops don’t get asked whether they’ll be drinking their coffee on site or taking it with them to go. However, many leading coffee shops in the United Kingdom find out that detail from customers who order drinks, then serve the beverages in non-disposable mugs to people who’ll enjoy their purchases on the spot.

Also, all 950 Starbucks locations in Great Britain recently began charging customers five cents for getting their drinks in disposable cups. Conversely, it rewards them by taking 25 cents off the costs of their orders when they bring reusable cups into the stores.

Creative Ways to Cut Down on Farm Waste

Manure (or fertilizer) is a reality on farms around the world. And, the commercially bought versions of it contribute to excessive waste and inflated costs. Some even harm future growth when farmers apply manure too heavily and negatively affect the soil’s balance.

But, besides avoiding commercially-sold manure and not applying it excessively if used, what else can people in the agriculture sector do to make farm waste more manageable? They can look for unique outlets that may want to buy it.

One startup uses a detailed manure-refining process to extract the cellulose from cow dung. Business representatives then use the cellulose — a byproduct from the grass and corn cows eat — for a new kind of fabric.

What about using animal waste for energy? A forward-thinking farmer did that with his manure lagoons, making them produce biogas that powers homes.

These unusual solutions highlight unconventional use cases for animal droppings, such as poultry litter, that support zero-waste goals, provided farmers want to explore them.

An Uptick in Reusable Food Containers

People often pack their lunches in plastic containers before heading off to work, but when they get food delivered or pick it up from a provider to eat at home later, the associated containers usually fill up garbage cans after people chow down.

Some facilities are trying to change that. At The University of California Merced campus, a pilot program occurred where students who stopped by dining halls for meals to take away brought reusable containers with them. After people ate the food from them, they could return them to get washed and ready for future meals.

Moreover, a pizza restaurant in Wales provides an aluminum box for people to use again and again when taking their pies home. One of the problems with cardboard pizza containers is they can’t be recycled when contaminated with grease. However, people can buy the metal ones for a small, one-time fee.

Opt for reusable containers for food and beverages

Then, by using them, they get 50-cent discounts on their pizza. The restaurant also backs the boxes with a lifetime guarantee and will replace them for no charge if necessary due to breakage or damage. Also, because metal conducts heat, the material helps pizza stay hotter for longer than it would in cardboard boxes.

Innovations to Complement Commitment

Adhering to a zero waste lifestyle undoubtedly requires dedication and a willingness to look beyond old habits. However, for people who show those characteristics, numerous inventions and improvements make it easier to do away with the throw-away culture.