How would you define renewable energy in terms of energy flows
harnessing natural energy flows in the biosphere.
Organic materials of recent biological origin.
A bioeconomy provides society with essential sources of carbon and energy from agriculture
4 motivations for returning to a bioeconomy
- 1. Improving environmental quality
- 2. National security (reducing reliance on imported petroleum)
- 3. New markets for producers (reducing excess agricultural production)
- 4. Rural development (opportunities to boost jobs and net income)
What are the five challenges in working with solid biomass?
- 1. Low bulk density
- 2. High moisture content
- 3. High oxygen content
- 4. Relatively low heating values compared to hydrocarbons
- 4. Handling systems more complicated and less dependable compared to systems for liquids and gases.
two major categories of dedicated energy crops
- 1. Terrestrial species
- 2. Aquatic species
What are the five “building blocks” from biorenewable resources?
- 1. lignin
- 2. carbohydrates
- 3. chitin
- 4. lipids
- 5. proteins
How much biomass could be produced annually in the United State?
1 billion tons annually
What are the three categories of bioenergy?
- 1. Process heat,
- 2. biopower,
- 3. biofuels.
What are the two categories of biobased products?
Approximate each of the following systems as isolated, closed or open systems over “short times”
- 1. Heating a brick in the sunlight: Closed
- 2. A boiling teapot: Open
- 3. Coffee in a thermos bottle: Isolated
- 4. The Planet Earth: Closed
- 5. The Universe: Isolated
Characterize each as approximately unsteady or steady flows (including quasi-steady)
- 1. An idling engine: Steady
- 2. An injection from a hypodermic syringe: Unsteady
- 3. A boiling tea pot: Unsteady
- 4. The body’s circulatory system: Steady
Explain how a general mass balance is performed
- 1.draw C.V.
- 2. draw inlets and outlets of mass flow
- 3. An ordinary differential equation is written that indicates the rate of change within the control volume is equal to the sum of mass flows entering minus the mass flows exiting
Why can’t we define yield Y on a molar basis as Y=moles of product/moles of reactant?
Whereas mass is conserved in a reaction, moles are not. Thus, we must consider changes in moles in terms of stoichiometric limits of the products. This is done with the stoichiometric factor.
- Ratio of the amount of desired product to amount of reactant converted.
- desired product:amount of reactant converted
energy efficiency, energy return on energy investment (EROEI), and explain the difference between them.
- Energy Efficiency: useful energy out/(energy expended + energy in feedstock being processed)
- EROEI: useful energy out/energy expended
- EROEI is meaningful for extractive processes that do not consume the extracted resource (oil drilling or biomass harvesting, for example). It is not particularly useful for processes that consume a feedstock (reactant) to produce a product, resulting in ratios that are unbounded and misleading.
How should you respond if someone asks if “it takes more energy to manufacture biofuels than is found in the biofuels?”
- : Of course - and it is true of all energy carriers (fuels) that we produce from primary energy sources.
- Otherwise, the second law of thermodynamics is violated.
Some people argue that thermochemical processes are wasteful of energy because they are endothermic – energy must be added to the reactants to get products. What is wrong with this argument?
Much of the energy going into an endothermic reaction ends up as chemical energy of the products, which is anything but wasteful. In fact, production of fuel by an exothermic process is more likely to dissipate low temperature heat, which is waste energy.
In subsequent discussions of processing of biorenewable resources we will rarely refer to equilibrium– why is that?
Kinetics rather than thermodynamics determine the extent of reaction in many real processes.
What kind of biomass material contains large amounts of aromatic compounds?
What stands in the way of this kind of biomass being used in fuel production?
Large amounts of oxygen compared to hydrocarbons currently used as fuel.
Why does it take so much energy to distill ethanol from beer (alcohol-water mixture produced from fermentation of sugar)?
- Hydroxyl grps have large intermolecular forces due to :
- A. high boiling points
- B. high solubility in water
Which classes of carbohydrates can be directly fermented by microorganisms?
- 1. monosaccharides
- 2. some disaccharides
What distinguishes aldoses from ketoses?
Aldoses contain a single aldehyde group while ketoses contain a single ketone group.
The number of carbon atoms in monosaccharides can range from 2 to 7. Which kinds (in terms of carbon atoms) are found in structural and storage polysaccharides?
How can we utilize polysaccharides?
Hydrolyzing them to mono- or disaccharides suitable for fermentation.
why lignocellulose so hard to deconstruct to sugars?
- cellulose: has highly crystalline structure lignin:
- both of these prevent acids or enzymes from penetrating lignocellulose structure.
What is the theoretical attractiveness of lignin compared to cellulose and hemicellulose?
Its relatively low oxygen content makes it closer to hydrocarbons currently processed by the petroleum/petrochemical industry.
What are the six crop categories of interest to bioenergy
- 1. oleaginous biomass (terrestrial)
- 2. woody
- 3. aquatic
- 4. sugar crops
- 5. starch crops
- 6. herbaceous
What is the main attraction of oleaginous biomass and what is the main disadvantage of the current generation of such crops?
- 1. easy to process the hydrocarbon material
- 2. the oleaginous material is low yielding
What characterizes herbaceous crops?
They contain little or no woody tissue.
herbaceous plant pros over woody
easy to delignify
What are major differences between hardwoods and softwoods?
Hardwoods are angiosperms – flowering plants – whereas softwoods are gymnosperms – deciduous (evergreens)
What does the relatively low content of lipid for many forms of algae imply about its processing?
Large amounts of byproduct will be produced, which must be productively utilized.
Why is proximate and ultimate analysis important to processing of biomass?
- Proximate analysis is important in thermochemical processing, indicating how much moisture and volatiles will be released and how much carbonaceous and inorganic solids will be produced.
- Elemental analysis is important for mass balances on C, H, and O, in particular.
Why is alkali content of biomass important to combustion applications?
Alkali is responsible for ash fouling and boiler tube corrosion during combustion.
What are the implications of the relatively low volumetric energy density of biomass?
Large centralized plants will have enormous transportation and storage challenges.
What limits the removal of stover from harvested fields?
Soil erosion, soil carbon loss, and nutrient replacement costs.
How does agriculture influence carbon loss?
1.cultivation thru erosion and mineralization (oxidation)
How has agriculture through history and around the world maintained nutrients in the soil?
- 1. Early agriculture :manure, seaweed, and grew “green manure” to maintain fertility.
- 2. More recently: ammonia from Haber-Bosch process used to replace nitrogen and phosphate mined from fossil deposits.
What makes most sense for expansion of biofuels agriculture: row cropping or perennial forage crops?
- Perrenial bc:
- 1. less pesticide use
- 2. less tillage that causes less mineralization
- 3. less erosion bc of the perrenial root system
Where in the world is the “best opportunity” for growing biomass?
The tropics have plentiful sunlight and water as well as urgent need for improvements in human development.
Pros for woody biomass for biofuels compared to herbaceous biomass?
Storage “on the stump;” higher energy density; less tendency to decompose in storage.
What are some of the key challenges in storing biomass?
Large areas required for storage, preventing decomposition; avoiding fires.
What are the key challenges to cultivating and harvesting microalgae?
Getting sunlight, carbon dioxide, and nutrients to microalgae; harvesting at 0.05% solids in water; removal of water from sludge.
What are the two main cultivation approaches for land-based microalgae production?
- 1. Open raceway ponds
- 2. closed tubular photobioreactors.
What are some specific examples of GM plants in agriculture?
BT (insect resistant) corn; Roundup Ready (herbicide resistant) soybeans; Golden rice (Vitamin A fortified); Extended Freshness tomatoes.
Give two examples of process heat applications
1.Home heating; hot water; baking; drying grains/malt.
With what does biomass have to compete for process heat applications in the United States?
What do we mean by biopower in this course?
Biopower is the use of biomass for the production of stationary electric power (as opposed to “powering” and automobile with biofuels).
Which power cycles are most relevant to biopower applications?
Rankine (steam) and Brayton (gas turbine)
Which power cycles are most relevant to automotive applications?
- 1. otto (spark ignition)
- 2. diesel (compression ignition)
Explain the overall performance advantage of blends of molecules vs a single kind of molecule for automotive fuels
Can tune the fuel properties for desired cold-start performance, environmental performance (VOC emissions), or type of engine (spark ignition vs compression ignition).
What is the key feature of a fuel for use in spark-ignition engines? In compression-ignition engines?
- 1. spark ignition: octane #
- 2. cetane number
Beyond ignorance, what are two objections to using blends of ethanol with gasoline (in terms of performance issues, not environmental concerns)?
- 1. Lower volumetric heating value (miles per gallon you can drive);
- 2. water-induced phase separation of gasoline and ethanol.
What do most petrochemical building blocks have in common?
They are hydrocarbons as opposed to oxygenated organic compounds like carbohydrates.
List two things that discourage the use of biorenewable resources for the production of organic chemicals currently derived from petroleum.
- 1. Chemicals produced from biomass are usually more expensive than those derived from petroleum;
- 2. current organic chemical industry based on hydrocarbons whereas biomass starts with highly oxygenated compounds.
Characterize the difference between a natural biopolymer and a synthetic biopolymer?.
- Natural biopolymers are fibers produced in nature while
- synthetic biopolymers are synthetic fibers produced from biorenewable chemicals
Explain why all biodegradable fibers are not necessarily biobased fibers.
Biodegradable refers to the fact that the fibers can be degraded by biological processes such as composting. These may be produced from petroleum or biorenewable resources.