Renewable Energy 6 – Biomass energy systems

Burning wood is probably one of the oldest and most common forms of producing heat and energy.  Yet, as anyone who has ever sat around a campfire will attest, the smoke can be problematic.  Photosynthesis is one of the most incredible mechanisms in nature – diffuse light energy from the sun is captured and turned into concentrated chemical energy – the most common of which is cellulose.  Yet, the release of that heat and light causes the release of the chemical materials (carbon dioxide and ash – residues of all the other chemicals) in to the atmosphere.  Of course, some heavier ash is left at the site if combustion.  The obvious problem is that all biomass energy is a reverse of photosynthesis, yet that being said, it still has a lot of potential to power our systems and is completely renewable.  

There are basically four types of biomass in use today – Wood and agricultural products that accounts for about 44% of current biomass usage.  

  • Wood and biowaste from burning dead trees, and waste wood from places like wood mils, forest debris, building demolition sites, and even dried animal manure.  Many people in more affluent areas often have open wood fires that are both esthetically pleasant and can make use of dead wood.  In rural areas the pollution is not severe but in a large town or city would quickly come to produce the smoke smogs that were so devastating to health in the 1700s and 1800s.   Waste wood can be burned directly or it can be processed into smaller pellets for incineration in higher temperature boiler systems.  This is a way to ‘reuse’ wood products, but in the end it is simply an advantageous economic aspect of energy generation and does little to alleviate pollution problems. 
  • Alcohol fuels (like Ethanol or Biodiesel), that are derived from crops like corn and algae.  One of the big problems with using crops is that these are also our food supplies. It’s a strange choice – food or fuel.  In the USA we have a surplus of food, but many developing countries struggle to feed their people let alone think about using what food they do produce for fuel.  Add to the problem of developed countries financing fuel crop growing in these developing countries creates hunger problems for people.  Add to this the problem that growing these crops is also energy intensive technology.  Alcohol is a lot cleaner to burn than fossil fuels – although there is still some pollution – but when the total spreadsheet is framed for Alcohol fuels, the only real option worth considering is that of algal alcohol, but that is still in its infancy.   There is E85 fuel available but a main problem of alcohol fuels is that alcohol can be corrosive to components of an engines fuel injection system thereby requiring more stainless steel and erosion resistant components be added to the engine. 
  • Solid waste incineration (conglomerate biomass – waste to energy or energy from waste)has been around for a few decades.  At first it was a solution to the growing solid waste problem in that it burned trash in traditional coal burning electrical generation plants.  The problems with burning solid waste is that the mixture of materials includes plastics and a multitude of other chemically derived products.   If the waste is not burned at a high enough temperature the resulting emissions can form toxic byproducts that need further treatment making this a potential health and economic problem.  Strict regulations are required to ensure public health safety and sorting trash before it is burned can be a costly process.  One advantage of this is that the emissions tend to be carbon dioxide, which is less polluting than Methane emissions often found from simple biological degradation with a trash dump – the old now rapidly disappearing form of trash disposal in the developed world but still prevalent growing problem in the developing world. 
  • Landfill gas and biogas.  This energy option derived from the methane produced by biodegrading trash or biodegrading wet animal manure.   Most landfills today are aseptic in that degradation is limited because of the compartmentalized nature of how trash is now stored in landfills.  The trash is packed into the landfill and then surrounded by clay.  This restricts the oxidation biodegradation thus keeping the trash in its undigested form for long periods.  What degradation does occur is anaerobic and produces methane.  In order to safeguard the landfill from potential explosive ignition of methane pockets, methane pipes are added to the landfill to vent off the methane.  Rather than vent the methane, many landfills are now capturing the methane for energy generation.  This works for the developing world and big cities around the world because of the immense amounts of trash generated in a consumer society.  In the developing world, however, one of the biggest problems, especially in rural and remote areas is that of over use of wood fuel.  Deforestation has been almost catastrophic in this areas with locals walking many miles a day to find enough wood for cooking and heating.  These people generally tend to be more pastoral and have many animals and hence lots of wet animal manure on hand.  Relatively small Biodigestor units can be given to each family where the wet manure is kept in a sealed tank to digest anaerobically.  The resulting methane each day serves as both the cooking and heating fuel, thereby relaxing the demand for fuel wood.  This has benefitted these rural villages in economic and ecological ways as well.  The reduction of fuel wood use has allowed the depleted forest to regrow, and the time saved in not having to find fuel has given the women especially, time to devote to crafts they can sell at local markets to tourists.  The men have been reported happy with the resulting digested liquid organic sludge as it is a better fertilizer for their crops than simple manure.  Of course, this biogas from biodigestors can be scaled up to community level to produce methane for larger numbers of homes.

While biomass can be a boom for many areas, especially more rural and remote areas, it is difficult to see how it can be scaled up for industrialized systems.  While biomass is renewable it often just substitutes for a more polluting alternative.  It does have advantages in that it usually produces less pollution.  In developed countries, the use of biomass such as algae has a lot of promise to substitute for oil-based fuels without disrupting the existing infrastructure and so as a stop gap option is beneficial.  One of the big aspects of biomass is the incredible amount of non-crop cellulose to be found on the planet.  This has been a difficult problem to crack – how to use cellulose economically, because degrading plant cellulose is not easy. 

There is some recent research that could soon change that.  In a 60 minutes episode on January 6, 2019,  unlikely genius inventor Marshall Medoff talks about a new technique to break down Cellulose cheaply and economically viable.  As Marshall says about his work, “What I thought was, the reason people were failing is they were trying to overcome nature instead of working with it.”  “What MIT trained chemist Craig Masterman has done is help implement Medoff’s novel idea of using electron accelerators to break apart nature’s chokehold on the valuable sugars inside plant life – or biomass. The accelerators can break the cellulose down to simple sugars that cane be used for a myriad number of functions from fuels to foods, and the process can even break down plastics easily.  The process doesn’t disrupt existing infrastructure systems but complements them with low polluting alternatives. 

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