CO2 Respiration: Difference between revisions
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#Take half of the sample in a Ziploc bag | #Take half of the sample in a Ziploc bag | ||
#Weigh the sample + tare of the container (bag, tray, etc.) | #Weigh the sample + tare of the container (bag, tray, etc.) | ||
#To adjust sample moisture content to 50% (wet basis, w.b.), calculate the adjusted total weight from the following spreadsheet | #To adjust sample moisture content to 50% (wet basis, w.b.), calculate the adjusted total weight from the following spreadsheet (INSERT TABLE HERE) | ||
#In the example, add de-ionized water to bring the final weight to 432.056 g (If the initial weight is greater than the final calculated weight, then air-dry to adjust moisture) | |||
#Open the bag and place it into the incubator (set at 30 oC) for 24 h | |||
#Weigh the sample and readjust its moisture content to 50% again | |||
#Open the bag and place it back into the incubator (set at 30 oC) for 24 h more | |||
#Check the weight of the sample and readjust its moisture content to 50% | |||
==Titration Method== | |||
*To prepare sodium hydroxide solution (2M), follow the next steps: | |||
#Weigh 80 g of NaOH pellets | |||
#Collect 1-L of de-ionized distilled water in a 1-L flask | |||
#Add approximately 500-mL of the de-ionized water into a 2-L flask | |||
#Add the sodium hydroxide pellets into the de-ionized water | |||
#Dissolve completely, add the de-ionized water to 1-L, stopper tightly, keep to cool | |||
*Place twenty grams of homogenized compost sample in a 150 ml beaker | |||
*Place twenty ml of NaOH (2M) in another 150 ml beaker | |||
*Place both beakers in a wide mouth 3.7-liter jar | |||
*In two 3.7-liter jars, place an empty 150 ml beaker and 20 ml of NaOH (2M) in another 150 ml beaker in each. | |||
*Screw the jars led tightly to prevent any gas exchange | |||
*Place all jars in the incubator for 48 h | |||
*The CO2 evolved during microbial respiration is bound by the alkaline absorbing agent according to the following chemical reaction: | |||
<math>CO2+2NaOH-->Na2CO3+H2O</math> | |||
*Collect the NaOH solution in small bottles. Mark the bottles and make sure they are tightly covered | |||
*In the Soil and Tilth Lab, follow the instructions to calibrate the titration machine and run samples including the blank | |||
*Calculate the carbon dioxide - carbon resulted from the titration method as follows: | |||
<math>CO2-C=(B-V)*N*E*(Tr/A)</math> | |||
**Where: | |||
**CO2-C is the evolved carbon dioxide-carbon [mg] | |||
**B is the volume of acid needed to titrate blank [ml] | |||
**V is the volume of acid needed to titrate sample [ml] | |||
**N is the normality of acid used for titration [-] | |||
**E is the equivalent weight to convert to mg [C = 6] | |||
**Tr is the trapped volume (20) [ml] | |||
**A is the aliquot titrated (1) [ml] | |||
*Divide the CO2-C by the volatile solids content (10 g solids x VS/100) in the sample and by the number of days (2) to calculate the CO2-C in mg/gvs.d |
Revision as of 11:43, 29 December 2011
Back to Protocols
Determination of Compost Respiration Rate
The main objective is to determine the microbial activity by measuring respiration rate in a compost sample. Two methods to determine the compost respiration rate, Titration and OxyTop, will be discussed below.
Sample collection and Preparation for Titration and OxiTop Methods
- Collect a composite compost sample
- Determine the sample moisture content and volatile solids content
- Place samples in freezer until needed
- Take samples from the freezer to the cooler, keep them for 24 h until samples completely thaw
- Take half of the sample in a Ziploc bag
- Weigh the sample + tare of the container (bag, tray, etc.)
- To adjust sample moisture content to 50% (wet basis, w.b.), calculate the adjusted total weight from the following spreadsheet (INSERT TABLE HERE)
- In the example, add de-ionized water to bring the final weight to 432.056 g (If the initial weight is greater than the final calculated weight, then air-dry to adjust moisture)
- Open the bag and place it into the incubator (set at 30 oC) for 24 h
- Weigh the sample and readjust its moisture content to 50% again
- Open the bag and place it back into the incubator (set at 30 oC) for 24 h more
- Check the weight of the sample and readjust its moisture content to 50%
Titration Method
- To prepare sodium hydroxide solution (2M), follow the next steps:
- Weigh 80 g of NaOH pellets
- Collect 1-L of de-ionized distilled water in a 1-L flask
- Add approximately 500-mL of the de-ionized water into a 2-L flask
- Add the sodium hydroxide pellets into the de-ionized water
- Dissolve completely, add the de-ionized water to 1-L, stopper tightly, keep to cool
- Place twenty grams of homogenized compost sample in a 150 ml beaker
- Place twenty ml of NaOH (2M) in another 150 ml beaker
- Place both beakers in a wide mouth 3.7-liter jar
- In two 3.7-liter jars, place an empty 150 ml beaker and 20 ml of NaOH (2M) in another 150 ml beaker in each.
- Screw the jars led tightly to prevent any gas exchange
- Place all jars in the incubator for 48 h
- The CO2 evolved during microbial respiration is bound by the alkaline absorbing agent according to the following chemical reaction:
[math]\displaystyle{ CO2+2NaOH--\gt Na2CO3+H2O }[/math]
- Collect the NaOH solution in small bottles. Mark the bottles and make sure they are tightly covered
- In the Soil and Tilth Lab, follow the instructions to calibrate the titration machine and run samples including the blank
- Calculate the carbon dioxide - carbon resulted from the titration method as follows:
[math]\displaystyle{ CO2-C=(B-V)*N*E*(Tr/A) }[/math]
- Where:
- CO2-C is the evolved carbon dioxide-carbon [mg]
- B is the volume of acid needed to titrate blank [ml]
- V is the volume of acid needed to titrate sample [ml]
- N is the normality of acid used for titration [-]
- E is the equivalent weight to convert to mg [C = 6]
- Tr is the trapped volume (20) [ml]
- A is the aliquot titrated (1) [ml]
- Divide the CO2-C by the volatile solids content (10 g solids x VS/100) in the sample and by the number of days (2) to calculate the CO2-C in mg/gvs.d