ABE 482Environmental Engineering in Biosystems.ppt

1、ABE 482Environmental Engineering in Biosystems,October 1 Lecture 12,Today,ALS results C/N ratio of sheep manure and silage piles Waste to energy calculation and discussion,ALS Results,Sheep manure and straw 240 lbs/ton total C 14.8 lbs/ton total N 60% moisture content 4.3 lbs/ton P 18.7 lbs/ton K 2.

2、6 lbs/ton S,Silage 241 lbs/ton total C 12.1 lbs/ton total N 58.4% moisture content 2.7 lbs/ton P 11.4 lbs/ton K 1.4 lbs/ton S,Total N is on a dry basis. All other values on a wet basis.,Waste to Energy Calculation 1,Calculate the $ value of the electricity produced if all the MSW waste and manure wa

3、ste produced in Canada each year was anaerobically digested. 25 million wet tonnes of MSW/year 132 million wet tonnes of manure/year 30% dairy cow 30% beef cow 20% pig 20% other Assume digester runs 365 days a year, 24 hours a day Assume you can sell electrical energy for 14 cents/kW-hr Assume you c

4、an convert methane to electricity with an efficiency of 32% How many Canadians will this serve?,Use: Table 1 from lecture, ASABE standards for manure composition, internet for electricity consumption of Canadians.,Required Information/Assumptions,Biogas production per kg DM (Table 1 in notes) Averag

5、e MC of MSW and manure (ASABE standards and proportion of manure stated in question) Percentage of biogas that is methane Energy consumption of Canadians,Discussion/Limitations,Because energy consumption (kW-hr per year) is based on continuous use, we have to assume were continuously generating ener

6、gy from the biogas Estimates of DM content and biogas production per kg DM make a huge difference in final value!,What if the material was gasified instead?,Gasifier mass balance Inputs Feedstock Feed gas Outputs Fuel gas Tar Ash Heat + steam,Value of Digestate from Anaerobic Digesters,Typically, a

7、CSTR will result in Reduced DM by 25.6% Reduced total-N by 0.8% Increased inorganic-N by 25.7% Increased P2O5 by 0.7%,Waste to Energy Calculation 2,You have 50,000 kg of pig slurry at 4% DM, 4 kg/m3 total N, and 2 kg/m3 P2O5. Nitrogen is valued at $1.32 per kg and P2O5 is valued at $0.84 per kg. You

8、 have 2 options Land apply raw slurry Anaerobically digest slurry and land apply digestate and sell excess power to the grid Assume specific gravity of slurry is 1. Assume the slurry will generate 0.625 m3 of biogas per kg DM (60% methane) and that the digester requires 1850 kW-hr of energy to opera

9、te. Assume you can sell excess power for 14 cents per kW-hr.,Which option provides the highest revenue?,Waste to Energy Calculation 3,You have been hired to assess the viability of producing natural gas from cull potatoes from a processing plant in south-central Saskatchewan. The potato processing p

10、lant produces 500 tonnes of potatoes per day, 15% of which are classified as cull potatoes for which there are no markets. Given the following information, calculate What volume of natural gas (CH4) could be produced? How many vehicles could be supplied with compressed natural gas fuel? If the gas w

11、as used to fire a generator, how many kW per day could be generated? How many homes could be supplied with power?,Waste to Energy Calculation 3,Information: Raw potatoes are 80% water and 20% solids 35% of the solids are starch Anaerobic digestion converts startch glucose (C6H12O6) CH4 + CO2 The gas

12、 produced is 60% CH4 and 40% CO2 by volume The density of CH4 = 0.6 kg/m3 and of CO2 = 1.4 kg/m3 SaskEnergy has found that 1 m3 of CH4 is equivalent to 1.059 L of compressed gas The average vehicle holds 80 L of gas, travels an average of 70 km per day and uses 8 L per 100 km Natural gas has an energy value of 37,320 kJ/m3 A gas fire generator is 72% efficient (i.e. it can produce 72 kJ of energy for each 100 kJ received from the fuel) The average home uses 35 kW of energy per day,Next day,Biogas measurements from digester lab,