Biomass Energy

In 2012 biomass energy accounted for about 5% of the energy used in the United States. I’ll talk about what biomass energy is, discuss the various forms and sources, and then talk about how it fits into our home energy picture and how it can be used to save money.

GRASS, COWS & US

Using water, carbon dioxide, and some nutrients from the soil, grass converts solar energy into chemical energy through the process of photosynthesis.  This process produces sugars that the plant uses to grow, and a by-product that we humans love, called oxygen.  The grass lives through its life cycle and then dies.  After dying, the energy stored in the grass is released slowly over time.

What is Biomass graphicCows love energy so they use their mouths to mow and chew fresh grass.  The cows use the energy to grow, produce more cows and milk and make manure with some off-gassing as a by-product.  All good stuff in the scheme of things!

People love energy too so they grow grass and raise cows, drink the milk and eat the cows.  In this way, energy passes up the food chain.  You get the idea.

Biomass energy is the energy retrieved from plants and animals.

Decay, rotting, stinky gas – these are some of the words associated with the source of biomass energy.

Here’s another way to look at what biomass energy is.  Think of plants and animals as batteries that convert and store solar energy – solar batteries so-to-speak.  We produce biomass energy by retrieving energy from these solar batteries.

TYPES OF BIOMASS

Any decaying plant or animal carcass can be a potential source of biomass energy.  However, there are 5 main types of biomass.  You’ll see the types categorized in different ways in various literature, but these items are always associated with biomass energy.

1) WOOD

About 45% of all biomass energy comes from burning wood.  Burning of wood logs, wood chips or sawdust releases heat and that heat is either used directly for heating or converted to another form of energy like electricity.

2&3) CROPS AND ALCOHOL FUELS

The gasoline we use in our cars is typically about 10% ethanol and 90% gasoline, known as E10.  Most ethanol produced in the United States is made by fermenting and distilling corn.  Sorghum, barley, sugar cane, sugar beets, rice, grasses, bark or potato skins can also be used, but corn has become an especially large cash crop in the Midwestern U.S. to produce ethanol for mixing with gasoline.  Ethanol is an alcohol biofuel that burns cleanly, so mixing it with gasoline reduces pollution and helps auto manufacturers meet emission regulations.

Types of BiomassSome states, mostly in the Midwest, have greatly increased the percentage of ethanol in fuel.  Ethanol is very corrosive to fuel systems so auto manufacturers have had to change the materials used for fuel lines, fittings and injection systems to work with it.  Cars that are capable of running on various percentages of ethanol and gasoline are labeled “flex fuel”, referring to their ability to run on anything from pure gasoline to E85, which is 85% ethanol and 15% gasoline.  All cars and light trucks manufactured in the 2007 model year and newer are capable of using up to a 15% ethanol mixture, or E15.  Older vehicles can still burn E10 or E15 but there is no guarantee that their fuel systems will hold up over the long term.  It is not normally a problem as long as you stick with ethanol mixtures of 10% or less.  But ethanol mixtures greater than 15% require flex-fuel vehicles.

When burning greater than 15% ethanol in gasoline, not only do all fuel system parts have to be designed to withstand the corrosive effects of ethanol, but engines have to be tuned to run smoothly on fuel with a lower energy content.  This is the disadvantage of ethanol as a fuel.  It reduces engine efficiency, power, and gas mileage.  So the clean-burning advantage must be tempered by the fact that it does not contain as much energy for a given volume as petroleum gasoline.  That and the fact that ethanol is more expensive than gasoline is the reason we don’t typically burn higher percentages of the alcohol in our fuel.  Studies show that E10 fuel reduces gas mileage by about 3.7%, E15 reduces it by about 5.1%, and E20 reduces it by about 6.5% as compared with burning pure petroleum gasoline (E0).*  It’s important to realize that EPA gas mileage data is compiled using E0 fuel, i.e., no ethanol.  So their mileage figures will always be a bit higher than the mileage we get using the typical E10 fuel found at most gas stations today.

Biodiesel is a fuel that can be used to replace petroleum diesel fuel.  It can be made from animal fats, greases including discarded restaurant grease, rapeseed, and vegetable oils.  But most biodiesel is made from soybean oil.

Biodiesel is most often designated B2, B5, B20 or B100 where the number signifies the percentage of biodiesel in the mixture, the remainder being petroleum diesel.  An appealing characteristic of biodiesel is that it can be used in 18-wheelers and most diesel engines without any changes to the engines or fuel systems.

Still, another biomass fuel is algae.  Much research is currently being conducted to find efficient methods of growing and refining algae into fuel.  I have high hopes that algae will supply a portion of our fuel in the future.  It has many advantages over traditional biomass crops including:

  • Like other biomass sources, algae absorb carbon dioxide as it grows and then releases it when burned as a fuel.  This makes it nearly carbon neutral over its life cycle –  ideal to help mitigate the greenhouse effect.
  • Fuel made from algae can be used throughout our existing gasoline infrastructure (pipelines, transport systems, gas stations, cars, trucks, etc.) because the carbohydrates, oils, and proteins that it is composed of creates a fuel very similar to gasoline.  It can be burned in engines today without the high cost of building a new fuel infrastructure.
  • Algae is 5 to 10 times more efficient at converting sunlight into biomass than the more traditional crops like corn or sugar beets.
  • Algae actually clean pollutants like nitrates and phosphates from water by absorbing them as it grows.
  • And algae grows in salt water so it doesn’t require cultivation of valuable land that can otherwise be used to grow food.  The ocean becomes the garden.

Photo of garbage bags4) GARBAGE

Garbage plants or Municipal Solid Waste plants can be found in some large cities.  Garbage is burned and the heat is used to make steam.  The steam is then used to heat buildings or to run turbines that turn generators to make electricity.  Even though these plants are expensive to operate, the fact that they reduce the volume of waste that needs to be discarded in landfills by about 85% offsets the cost and makes them feasible in some areas.

5) LANDFILL GAS

Picture of landfillStinky, smelly, rotting garbage with animal and human waste releases methane (natural gas is 80-99% methane).  Landfill methane or biogas is conveniently concentrated in our landfills, and everybody has one nearby!  It makes sense to collect this gas and burn it for heat or convert it to another form of energy.  Because methane is colorless and odorless, it can be dangerous so new regulations require landfills to collect methane gas to mitigate safety and environmental concerns.

Landfill gas comprises about 11% of the biomass energy the United States and collecting it from landfills reduces energy waste and greenhouse emissions.  I’ve written a blog specifically about this form of biomass energy.  See Biomass Energy from Landfill Methane.

SO HOW CAN I USE BIOMASS ENERGY AT HOME?

Now that we’ve talked about what biomass energy is, where it comes from and how it can be used, let’s look at possible ways to use it in our homes.

The truth is that biomass requires large quantities of ingredients to make a useful quantity of fuel.  It takes large fields of corn, lots of garbage from a city, and big landfills to produce enough methane or ethanol to be useful – not something most of us have access to.

So, for most of us, biomass energy will be part of our lives in two ways:

  1. Mixed with the gasoline we buy.  Most gas stations today sell unleaded E10 gas so we really have no choice but to use some biofuel in our vehicles.
  2. Burning wood.  Wood is the most common biofuel and it is most often burned for heat in wood stoves or fireplaces.

FIREPLACES

Fireplace photoThe vast majority of fireplaces are simply not energy efficient.  In fact, they often have an overall negative effect on home efficiency because of the chimney effect that tends to suck the interior air out of the house, losing cooled air in the summer and heated air in the winter.  When not using a fireplace be sure to close the chimney damper and ensure that it has a good seal.  In most fireplaces, sticking your head into the fireplace on a sunny day and looking up is a good way to check the damper.  If you see daylight around the damper you know there is air leakage.  A little is ok, but you should only see cracks of light around the very edge of the damper.

The same holds true for popular gas burning fireplace inserts and ceramic logs.  They look great but are a poor use of gas for heating because of their inefficiency.

Use the furnace to heat the house and use the fireplace to add a warm aesthetic appeal to a room.  Curling up on a couch with your sweetheart in front of a warm fire will make the inefficiency of a fireplace seem just fine!

WOOD STOVES

Wood stove photoWood stoves are far more efficient than fireplaces.  In fireplaces, most of the heat rises up the chimney and escapes outdoors.  Wood stoves radiate heat in a room from the body of the stove itself and also from the vent pipe in the room.  The vent pipe is usually single wall in the room so it radiates maximum heat, and then it becomes double or triple wall before it penetrates a wall or ceiling to provide fire protection.

Modern wood stoves also have a vent pipe to bring in outside air for combustion.  This means they don’t have to suck warm air from the room to feed the fire, making them even more efficient.

The Environmental Protection Agency has mandated air pollution limits which have resulted in more efficient wood-burning stoves.  The stoves today are generally 65% – 75% efficient – not bad for an inexpensive wood burner.  Efficiency is increased by controlling burning temperatures for maximum combustion of the wood and using catalytic converters as a secondary burner to burn any unburned hydrocarbons that remain, not unlike the catalytic converter on the exhaust system of your car.

Wood pelletsA variation on the wood burning stove is the pellet stove.  These are wood stoves that burn wood pellets.  By controlling the size, moisture content and composition of the pellets, the stoves can be finely tuned to extract more heat from the combustion process, resulting in efficiencies over 80%.  Pellet stoves and the pellet fuel they burn are more expensive than standard wood stoves but their higher efficiency is attractive.  Whether they make sense for you depends on your budget and access to the pelletized wood fuel they require.  Wood pellets are often made from waste wood at mills and are not readily available everywhere.

There is one other type of wood-burning appliance I want to briefly mention – biomass boilers.  They are not common in the United States but other countries including many European countries have a significant number of installations.  These appliances burn wood to heat water – essentially a wood-burning water heater.  They have efficiencies greater than 90% making them a good choice when other fuels are not available. Click here to read an article which discusses whether biomass boiler costs are justified, or perform a search on Google to learn more about this type of boiler.

Wood burning stoves are much less efficient than newer gas and oil furnaces, but they have a place in areas with abundant firewood and in remote areas that don’t have access to other fuels.  If you buy one, get the most efficient unit you can find and I think you’ll be quite happy with it.  And remember, except for the aesthetic appeal, wood burning stoves are far superior to any fireplace.  And a wood stove nicely designed into a room can be quite aesthetically appealing, giving you the best of both worlds while burning biomass wood efficiently.

I wrote a blog comparing the cost of heating your house with a wood-burning stove to heating it with a natural gas furnace. Click here to find out which was more expensive.

SAFETY FIRST!!

Fire safety is extremely important with fireplaces and especially wood stoves.  Please be careful!  Keep these tips in mind:

  • Fire extinguisherAll stoves with a single wall must be installed at least 36 inches from combustible surfaces.  Stoves with less than 36 inches clearance must have a double wall and there will be a metal tag attached to the stove with the manufacturer’s required minimum clearance on it.
  • Single wall vent pipe must be at least 18 inches from combustible surfaces.  Only use single wall pipe in open rooms you are trying to heat.  It helps extract as much heat from the flue gas into the living space as possible.
  • Always use triple wall vent pipe or chimney pipe in penetrations, inaccessible areas, and outside the room being heated.  Maintain at least 2 inches clearance to combustible surfaces.  Check penetrations and attic areas for clearances.  Lack of clearance in penetration and attic areas is a common source of house fires.
  • Clean stove vents and chimneys periodically to avoid combustible build-up on the interior surfaces.  This is especially important when burning soft woods with a high sap content.

Remember – always follow codes and manufacturer recommendations, use common sense, and be safe!

IS BIOMASS ENERGY RENEWABLE?

Most people will agree that the majority of biomass energy is renewable because you can always grow more trees and corn or other crops.  And animals keep eating, pooping, reproducing and dying.  However, there is some contention as to whether biomass energy from garbage or landfills is renewable.  In my view, it is not renewable.  I agree that there will always be garbage in the foreseeable future, but my point is that we need to minimize and eventually eliminate garbage by recycling it in ways other than letting it rot in a landfill.  Creating trash is not ultimately a sustainable practice and it is something we should minimize.  So let’s call garbage and landfills semi-renewable, definitely utilize the methane produced, and always work to minimize it.  Other biomass energy is definitely renewable.

HOW TO SAVE MONEY WITH BIOMASS ENERGY

Unfortunately, most biomass energy is expensive energy.  For most of us, burning wood is the type of biomass most likely to be economical.  Read my blog here to find out whether wood or natural gas is more expensive to heat your house.  In the blog you’ll learn how to determine the least expensive solution for your particular situation.


* Oak Ridge National Laboratory, Pub 31271, Page 48