PHYS 1110

Lecture 21

Professor Stephen Thornton

November 15, 2012

Reading QuizWhich plant has a great future in most of the US in producing biofuel generated electricity?

A) Pine treesB) RosesC) English ivyD) SwitchgrassE) Kudzu

Reading QuizWhich plant has a great future in most of the US in producing biofuel generated electricity?

A) Pine treesB) RosesC) English ivyD) SwitchgrassE) Kudzu

Quiz on solar (Ch. 7) and wind energies (Ch. 8) today.

Homework 5 on Ch. 8 due today.

Bioenergy is a term that represents the use of material having a vegetable or biological origin that is used as a source of energy. It takes many forms including biomass, biofuels, and biogas.

Bioenergy is a renewable energy because its energy comes from the sun. Biomass can regrow over a relatively short time period, and by the process of photosynthesis, chlorophyll in plants captures the sun’s energy by utilizing CO2 from the air and H2O from the ground to produce carbohydrates – complex compounds composed of carbon, oxygen and hydrogen. Energy is released when these carbohydrates are burned, and they turn back into CO2 and H2O. Biomass acts as an agent for storing the sun’s energy until it is needed.

Biomass is an organic nonfossil material of biological origin. Biomass supplies an increasing amount of electricity and heat and provides the majority of heating produced by renewable sources. An estimated 62 GW of biomass power capacity was available by the end of 2010.

Energy crops can be grown in large quantities, particularly on marginal lands, on pastures, or as double crops that fit into rotations with food crops. Native trees and grasses are particularly useful, because they often require fewer synthetic inputs and pose less risk of disruptions to the ecosystems. Thin-stemmed perennial grasses formerly blanketed the prairies of the United States before settlers replaced them with food crops. Switchgrass (left) and Big Bluestem (right) grow quickly in many parts of the country and can be harvested for up to 10 years before it needs to be replanted.

Native growth of switchgrass throughout the United States and Canada.

One solution is to build power plants that can burn different kinds of fuel. Dominion Energy just opened a $1.8 billion plant capable of producing 585 MW in Southwest Virginia near coal mines in Virginia, WestVa, and Kentucky. A wood tipper system delivers waste wood in photo.

Crop residues: leaves; corn stalks are controversial because of ethanol production.Manure: use anaerobic digesters (biogas), combustion or gasification.Woody biomass: bark, sawdust, etc. Burn it.Forest residues: tree tops, branches, etc. Most should be left in place, but some can be burned.Better forest management would allow dead, damaged, smaller trees for energy.Urban waste: shipping pallets, leftover construction wood, tree trimmings, etc. Collect methane from landfills.

Converting biomass to bioenergy

Direct combustion: make electricity and use leftover heat. Fireplaces have ~10-30% efficiencies. Modern boilers have up to 90%.Cogeneration with coal.Repowering: Convert coal plants to biomass.Combined heat and power: see http://mn.gov/commerce/energy/images/DG-Kramer-koda-energy.pdf Landfill gas: pipes inserted into landfill collect gas. See next slide.

Schematic of the Mountain Gate LFG Recovery System near UCLA in West Los Angeles, CA. Bottom: The beautiful Mountain Gate Country Club golf course covers the landfill.

Gas goes to 40 MW co-generation plant at UCLA.

Converting biomass to bioenergy

Pyrolysis: conversion of biomass to liquid, solid and gaseous fuels in absence of air at high T.Torrefaction: mild form of pyrolysis at lower T.Anaerobic digestion: Biochemical process – bacteria digest biomass in oxygen free environment to produce biogas. Dairy farms do it, produces heat and electricity. Done in Denmark and other European countries. Slide.Gasification: Conversion of biomass to gaseous fuel called syngas. See next slide.

Gasification process.

Sugar cane and rice residues are important crop residues. Because of their high silica content, rice hulls should not be burned or fed to cattle. However, rice hulls can be used to produce biogas through gasification.

QuizWhich part of the country is best for wood resources?A)Far westB)Rocky mountain statesC)SouthwestD)SoutheastE)Midwest

QuizWhich part of the country is best for wood resources?A)Rocky mountain statesB)Far westC)SouthwestD)SoutheastE)Midwest

QuizWhich of the following processes is perhaps not good for converting biomass to bioenergy?A)ParalysisB)Direct combustionC)Anaerobic digestionD)GasificationE)Cogeneration

QuizWhich of the following process is perhaps not good for converting biomass to bioenergy?A)Paralysis – don’t confuse pyrolysisB)Direct combustionC)Anaerobic digestionD)GasificationE)Cogeneration

World biofuel production in 2010

Considerable research and development is underway to use biomass, which is made of very complex sugar polymers, to produce ethanol, usually called cellulosic biofuels or sometimes cellulosic ethanol, which is the most widely discussed. Cellulosic ethanol is different from the corn ethanol, now widely available. Cellulosic ethanol is made from feedstock having no food value, but it potentially results in fewer greenhouse gas emissions and has a higher energy balance. It is more expensive to produce than corn ethanol.

The U.S. Energy Policy Act of 2005 included several measures to stimulate the demand for biofuels. Part of this act was the Renewable Fuels Standard (RFS) that requires that gasoline must include an increasing amount of renewable fuel, starting at 4 billion gallons in 2006, increasing by 700 million gallons a year and reaching a level of 7.5 billion gallons by 2012. The Energy Independence and Security Act of 2007 amended and increased the RFS, requiring 9 billion gallons of renewable fuel use by 2008, and reaching a value of 36 billion gallons by 2022. Under this revision, corn-based ethanol (conventional biofuel) is capped at 15 billion gallons by 2015, with 21 billion gallons by 2022 must be derived from advanced biofuel such as cellulosic and non-corn based ethanol. By 2022 16 billion gallons of the advanced biofuel is expected to be cellulosic biofuel, as in cellulosic ethanol.

Cellulosic ethanol shows great promise as a fuel, and the US. Government has provided more than a billion dollars towards its development. There is not yet a commercially viable operation, only demonstration projects. The cellulosic biofuel mandate established by Congress in 2007 stated there should be 100, 250, and 500 million gallons used by 2010, 2011, and 2012, respectively. The actual amount produced was only 6.6 million gallons in 2011. The EPA is required to lower the standards if they are not met, so the EPS lowered the RFS cellulosic biofuel mandate (actual volume) to 5, 6.6, and 8.65 million gallons for 2010, 2011, and 2012, respectively! The obstacles include unknown levels of feedstock supply, expensive conversion technology, and insufficient private capital. A 2011 National Academy of Science report mentions “the high cost of producing cellulosic biofuels compared with petroleum-based fuels and uncertainties in future biofuel markets”. The report mentions that technological breakthroughs are needed. The future is unclear.

Biomass contributed 3.6% to all energy produced in the United States in 2007, but less than 1% of that was for electricity generation. Most of it went to transportation fuels, primarily ethanol. Biomass was the greatest contributor to renewable energy in 2008, even larger than hydropower. By 2009 biomass was overtaken by wind energy, but biomass still contributed over 50 GWh of electricity, accounting for nearly 1.5% of the nation’s electricity. The US Department of Energy estimated in 2005 that the electrical generation capacity from bioenergy can be as high as 250 GW. This optimistic estimate assumes the country can produce more than a billion tons of biomass for energy use. The US Energy Information Administration estimated in 2007 that bioenergy could meet 12% of the nation’s electricity needs by 2025. The amount of available biomass estimated to be available for energy by 2025 varies widely and is highly optimistic.

The International Energy Agency is an autonomous agency with members from 28 countries, including the United States and other OECD members. It states that bioenergy is the largest single renewable source in the world in 2011, providing 10% of the global primary energy supply. This, of course, includes energy for cooking and space heating.

Global bioenergy electricity generated

As the global demand for electricity increases, the share of renewable electricity must also increase. The IEA hopes it will increase from a 19% share in 2009 to almost 60% by 2050. Bioenergy will have to play a significant role for this to happen and will have to increase ten-fold from 290 TWh in 2009 to 3100 TWh in 2050. The amounts by region are expected as shown with China accounting for the largest share.

The economics of bioenergy are expected to improve by 2030. The comparison varies as the size of the power plant and the cost of feedstock. Co-firing (cogeneration) is already cost competitive, and for lower feedstock costs and larger power plants, the costs overlap. There is no reason to expect that the feedstock costs are going to be so low.

From many standpoints bioenergy seems to have a promising future. But it is likely to be at least two decades before that future is realized. It has been said for the past decade that bioenergy is promising, but remember that corn ethanol took more than 20 years before it reached its level of today. Many skeptics still claim that corn ethanol cost more to produce than we pay for at the gasoline pump.

The cogeneration of burning biomass with coal currently seems to be the most promising endeavor, because of higher efficiencies and lower capital costs for retrofitting an existing coal power plant for burning 10% biomass.

QuizWhich of the following global areas has the highest amount of biofuel production?A)North AmericaB)South & Central AmericaC)EuropeD)AfricaE)Asia

QuizWhich of the following global areas has the highest amount of biofuel production?A)North AmericaB)South & Central AmericaC)EuropeD)AfricaE)Asia

Issues/problems

• Handling, transport, storage, feedstock.• Low efficiencies• Corrosion• High capital costs• Needs large scale demonstration plants• Competition of biomass with food, animal feed, electricity generation, and biofuel.• Sustainability (water)

Greenhouse gas emission (excluding land use changes) per unit output for a range of bioenergy and fossil fuels.

Advantages of bioenergy

• Bioenergy is a reliable renewable energy.• Can use organic waste that may be discarded.• Utilization of marginal land to grow feedstock.• Potential for being less expensive than fossil fuels.• Can be produced locally. • Creates local jobs.

Disadvantages of bioenergy

• Economics, economics, it’s the economy.• Biomass has lower energy content per mass than fossil fuels.• Labor, transportation, storage costs are high.• Water sustainability.• The competition for biomass between food, fuel, and electricity generation!

Disadvantages of bioenergy

• Economics, economics, it’s the economy.• Biomass has lower energy content per mass than fossil fuels.• Labor, transportation, storage costs are high.• Water sustainability.• The competition for biomass for food, fuel, and electricity generation!

Tidal Energy• Renewable• Two high tides a day• Need 4-5 m tide heights• Water rises steeply in estuaries, lagoons, rivers increasing height of water.• Estimate 3000 GW global, but only 60 GW potential

Tidal barrage

The first commercial tidal wave facility was constructed in Brittany, France on the estuary of the Rance River. It is a tidal barrage system. It began operation in 1966. It has 24 turbines that produce 240 MW of power. The second commercial plant was a tidal barrage system that was built at Annapolis Royale, Nova Scotia, Canada. It became operational in 1984 and produces 20 MW. It is the only commercial tidal barrage in North America.

Rance River estuary tidal barrage. 240 MW

It is doubtful if many more additional tidal barrages will be constructed, because estuaries are among the world’s most productive and sensitive ecosystems. Barrages present a barrier to navigation to both fish and boats, but lock gates like those used in canals can allow shipping. The reduced tidal range (between high and low tides) can destroy the inter-tidal habitat used by wading birds. Sediment collected behind the barrage can also reduce the volume of the estuary over time. Even though the largest tidal power station that began operation in 2011 in South Korea is a barrage facility, the seawall dam had already existed since 1994.

Bay of Fundy, Nova Scotia, Canada. Highest tides in the world, average 11 m.

See camera at http://www.novascotiawebcams.com/bay-of-fundy/halls-harbour-history.html

There are various ways to utilize the power of tides: tidal barrages, tidal turbines, tidal lagoons, and tidal fences.