Team:Hong Kong UCCKE/Results
Results
Result Calculation
Mass reduction test
% change of solid/total mass (%SC/%TC)
= (final mass - initial mass) / initial mass
% reduction of solid/total mass (%SR/%TR)
= (initial mass - final mass) / initial mass
% difference with control data (%-C)
= % reduction of solid/total mass - % reduction of solid/total mass(Control data)
Or
= % change of solid/total mass(Control data) - % change of solid/total mass
Times of pressure test
= AVERAGE(data 1,data 2)
Detergent test
After the emulsification test, the liquid column would be divided into two layers, the emulsified oil layer on top, and the water layer in the bottom
Emulsification index (E.I.)
= height of emulsified layer / total height of liquid column
In order to show and compare the detergent effect more clearly, we present the data in ratio with the negative control (water) and the positive control (1% concentration AXE detergent), thus getting the AXE power.
AXE power
0 = Detergent effect of Water (N.E.I.=0.48)
1 = Detergent effect of 1% concentration AXE detergent (P.E.I.=0.58)
AXE power = (E.I. - N.E.I.) / (P.E.I. - N.E.I.) = (E.I. - 0.48 / 0.58 - 0.48)
As a thicker emulsified oil layer means a larger degree of emulsification, the greater the E.I. and the AXE power, the better the detergent effect.
Experiment 1:Effect of sugar on the mass reduction of food waste after three months
Aim: to test if adding sugar can increase the rate of respiration
Hypothesis: addition of sugar can increase the rate of respiration
Table 1.1: Results of experiment 1
* :measured with the % reduction of solid/total mass
Table 1.2:Weeks of air pressure of experiment 1
Table 1.3:Results of detergent test of experiment 1
* :measured with the % reduction of solid/total mass
Table 1.4:Results of pH test of experiment 1
Table 1.5:Smell Change of experiment 1
Graphed data:
Graph 1.1:Influence of the addition of sugar on the reduction in total mass%
Graph 1.2:Influence of the addition of sugar on the reduction in solid mass%
Major Considering D.V.: Mass reduction
Discussion
Let’s first discuss the results of Rice and Vegetables. From graph 1.1 , both rice and vegetable samples shows an obvious increase(+10%) in the reduction of total mass after adding sugar. From graph 1.2, vegetable sample has the highest increase(+13%) in the reduction in solid mass, while rice sample also increased(+11%) in the reduction in solid mass. From table 1.2, the week of pressure of both rice and vegetables increased by 4 after adding sugar, which is more than double of that without sugar.
The reduction in mass is due to the breakdown of complex food waste polymers into simpler substrates,the consumption of food substrates by microbes, and the fermentation of food substrates by bacteria. While the accumulation of air pressure is due to the degradation of substrates into gases including carbon dioxide, hydrogen and methane. So the two reflects the rate of anaerobic digestion. By using them as a parameter,we can conclude the rate of anaerobic digestion of Rice and vegetable surely increased after adding sugar.
For the results of meat samples, graph 1.1 shows that the difference of reduction of total mass of meat sample with and without sugar is less than 1% ,so the effect of adding sugar is negligible. From graph 1.2, the meat sample with sugar have a lower(-14%) reduction in solid mass. However, the final solid meat sample collected is soaked with water, so we believe there is an error in measurement caused by the absorption of water of meat, and the data of solid mass can’t be taken into account. The weeks of air pressure of meat increased by 1 after adding sugar. Therefore, we believe the rate of anaerobic digestion of meat increased slightly after adding sugar, but the effect is not as good as vegetable and rice.
For detergent test, we used a ratio AXE power to test the sample’s cleansing property. The greater the AXE power, the better the cleaning effect.
From table 2, the cleansing effect of rice sample dropped by 0.43 after adding sugar. That of vegetable samples increased by 0.15 after adding sugar. That of meat samples dropped by 0.70 to -0.56 after adding sugar, which is half the cleansing property of water. So we can conclude that the addition of sugar greatly reduce the cleansing property of rice and meat samples. However, as we are still in the initial stage of finding ways of reducing mass, we decided not to take this into consideration.
The pH test gave us a brief idea that the pH of food waste samples generally hangs around 5. Only the pH of rice sample without sugar outstandingly reached 3, which is too acidic to be a detergent.
The Smell test of food waste is conducted weekly to observe the change. The smell of rice and vegetables don’t have much difference with and without sugar sugar. Rice sample gradually changes from a sugary smell to yeast and alcoholic smell. While vegetables continuously gives a strong sour vegetable smell. The smell of meat is improved after adding sugar. Without sugar, it gives out Fart, poop and vomit smell starting from week 3. With sugar, only sour meat and smelly meat is observed, but it is still unacceptable to be stored domestically.
Conclusion: The addition of sugar increases the rate of anaerobic digestion of the three food waste samples, especially rice and vegetables, so we decide to continue to use this condition in the following experiments. Though it has to be noted that the final product of rice is soaking with water and glutinous, and may not be suitable as a detergent.
Progress:
Experiment 2: Effect of changing temperature on the mass reduction of food waste
Aim: To test if increasing temperature can increase the rate of respiration.
Table 2.1: Result of experiment 2:
* :measured with the % reduction of solid/total mass
Table 2.2: Results of detergent test of experiment 2 :
Table 2.3: Results of detergent test of experiment 2:
Table 2.4: Results of pH test of experiment 2:
Graphed data:
Graph 2.1:Reduction in total mass% of food waste in different temperatures
Graph 2.2:Reduction in solid mass% of food waste in different temperatures
Major Considering D.V.: Mass reduction
Discussion
From the mass reduction test(table 2.1;graph 2.1,2.2), we can see that the rate of anaerobic digestion of all samples increased with a higher temperature. This is because in 37 °C, the reduction in total mass of all samples slightly increased(+2-5%), while the absorption of solid mass of rice and meat is greatly reduced(-20-25%). Of the three samples, Meat performed the greatest reduction with the increasing temperature. While vegetable performed the worst, with a much lower(-25.5%) reduction in solid mass after increasing temperature. However, from the soaking solid in the final results, we again believe this is an error in measurement due to the absorption in water. So the reduction of solid mass shouldn’t be taken into account.
For detergent test (table 2.2 ; graph 2.3), all samples showed the equally poor cleansing effect except for rice with higher temperature, which has an outstanding AXE power of 1.57. This is greater than the cleansing effect of 1% detergent by 50%, and higher than others by 140%, thus is remarkable.
The pH test ensured our observation in experiment 1 that the pH of food waste samples hangs around 5, Yet, it is notable that the pH of rice and vegetables increased by 1 after increasing temperature. So, there is a possibility that the increase in temperature creates a less acidic environment.
In this experiment, we didn’t take the smell test as we don’t expect much difference.
Conclusion: The increase in temperature increases the rate of anaerobic digestion, though the final rice product is still glutinous. Based on this and the outstanding improvement on detergent effect, we decide to continue to use 37 °C in our following experiments.
Experiment 3: Effect of yeast on the mass reduction of food waste after one month
Aim: To test if the addition of yeast will affect the rate of food waste digestion
Table 3.1: Result of experiment 3:
* :measured with the % reduction of solid/total mass
Table 3.2: Results of detergent test of experiment 3:
Table 3.3: Results of pH test of experiment 3:
Graphed data:
Graph 3.1:Influence of addition of yeast on the reduction in total mass%
Graph 3.2:Influence of addition of yeast on the reduction in solid mass%
Graph 3.3:Influence of addition of yeast on the cleansing property of the food waste
Major Considering D.V.: Mass reduction, Detergent Test
Discussion
From the mass reduction test, the effect of the addition of yeast on the rate of food waste digestion isn’t very constant. Only vegetables showed an increase(+7%,+14%) in both reduction of total and solid mass. Rice have an increase(+7%) in reduction of total mass but a great decrease(-20%) in that of solid mass, estimately inaccurate due to the absorption of water. While meat, on the contrary, decreased(-2%) in reduction of total mass but greatly increased(+31%) in that of solid mass.
> Conclusion: It can be determined that the addition of yeast increased the rate of respiration of vegetables and rice.
For detergent test, the cleansing effect of rice and meat reduced after the addition of yeast. The outstanding AXE power of rice from experiment 2 decreased by 0.40. Though it is still better than 1% detergent, but it is a huge stepback from our final goal of producing domestic detergents. While the poor AXE power of meat dropped to 0 to the same as water.
> Conclusion: Comparing the reduction in cleansing effect to the unconstant mass reduction, we decide to give up adding yeast in the following experiments.
The pH test shows that the addition of Yeast has no effect on the pH value. Yet, it ensured our observation in experiment 3 that the increase in temperature creates a less acidic environment with the set of Yeast data.
Experiment 4: Effect of the use of electric blender in preparation on the mass reduction of food waste
Aim: To test if the use of the electric blender in preparation process will greatly increase the mass reduction of food waste
Table 4.1: Results of Experiment 4:
*: measured with the % reduction of solid/total mass
Table 4.2: Results of pH test of experiment 4:
Graphed data:
Graph 4.1: Influence of the use of electric blender on the reduction in total mass%
Graph 4.2: Influence of the use of electric blender on the reduction in solid mass%
Discussion
From Graph 4.1 and 4.2, the reduction in total mass and solid mass of all three types of food waste increased after blending them with an electric blender in the preparation process. All increase in the reduction in solid mass is higher than that of total mass, which is reasonable as the use of blender mainly contributes to the first stage of anaerobic digestion - hydrolysis - the breakdown of solid.
Of the three types of food waste, the digestion rate of vegetables accelerated the greatest, with the highest increase(+27%) in the reduction of total mass, and a high increase of 47% in the reduction of solid mass.
Another thing worth noticing is that meat has the great increase(+116%) of over 100% in the reduction of solid mass. This is very worth noticing as we have never reached such a high reduction(81%) in solid mass, especially on meat which usually absorbs water. Yet, the reduction in total mass increased only slightly(+4%).
Although rice also increased in the reduction of mass after using blender, we note that it’s solid mass still seems to increase due to the absorption of water.
Conclusion: The use of electric blender increases the digestion rate of all three types of food waste, especially the breakdown of their solids. The use of blender also seems to resolve the problem of absorption of water of meat which makes the solution glutinous. Therefore, this shows the importance of mechanical work in food digestion, and we must try to include a blender in our machine prototype.
Experiment 5: Effect of fruit juice on the mass reduction of food waste after one month
Aim: To test the effect of fruit juice on the smell and rate of food waste digestion
Table 5.1: Results of Experiment 5:
* :measured with the % reduction of solid/total mass
Table 5.2: Results of detergent test of experiment 5:
Table 5.3: Results of pH test of experiment 5:
Graphed data:
Graph 5.1:Influence of addition of fruit juice on the reduction in total mass%
Graph 5.2:Influence of addition of fruit juice on the reduction in solid mass%
Discussion
From Mass reduction test, the addition of fruit juice has a slightly positive effect on the digestion of rice and meat.
From Graph 1 and 2,the solid mass of rice decreased to a large extent after adding kiwi and pineapple juice. Of the two,addition of pineapple have a much higher effect, with about 50% more solid reduced than the control set-up. While the total mass of rice reduced only slightly more than the control set-up, with about 4%. It is controversial that the 4% more reduced may only be the fruit juice added, but not helping the food waste respiration, so the increase is not taken into consideration.
For vegetables, adding fruit juice didn’t help reduce the solid mass much, only by 2% and 4%, while it even lowered the reduction of total mass by over 10%. Yet, we can spot that pineapple juice is slightly better than kiwi juice,as it reduced 2% more than kiwi juice does in both data.
For meat, it is interesting to spot that the reduction rate in solid mass and total mass of the three conditions are also much higher than the past experiments we made, reducing in 80% to almost 100% of the solid mass in only 1 month,instead of increasing due to absorption of water. We believe it is due to the different types of meat that we used in the experiments, yet it doesn’t really matter as long as we use the same in each experiment. Comparing the three, addition of fruit juice increased the reduction of solid mass by 17% to almost 100%, which is remarkable. Yet, for total mass,fruit juice didn’t show the same effect and even reduced less than the control experiment. This shows that fruit juice mainly helped break down solids into small bits or increase their solubility, but didn’t speed up the respiration of food waste into gas. Meanwhile, out of the two, Kiwi juice have a better effect on speeding up meat respiration from the data.
In conclusion, the addition of fruit juice increased the solid mass reduction rate of both Rice and Meat. Pineapple Juice have a better effect on Rice, while Kiwi Juice have a better effect on Meat.For vegetables, fruit juice inhibits its respiration rate instead. So we are considering to design the respiration process as the results.
Experiment 6: Effect of changing the ratio of food waste, sugar and water on the mass reduction of food waste
Aim: To test if the ratio of food waste, sugar and water will affect the rate of respiration of food waste
Table 6.1: Results of experiment 6:
Table 6.2: Times of pressure of experiment 6:
Table 6.3: Results of detergent test of experiment 6;
Table 6.4: Results of pH test of experiment 6:
Discussion
The meat samples are not included in the results as we failed to do it. The following discussion will only include the results of rice and vegetable samples.
For the mass reduction test (table 6.1), increasing the amount of sugar and water result in a greater reduction in mass of vegetable samples, although the percentage difference is not more than 10. Rice samples, instead, have a lower reduction in mass after adding larger amount of sugar and water.
For the detergent test (table 6.3), the samples that changed the ratios did not have a trend in a better or lower detergent effect, therefore it will not be discussed.
Experiment 7: Effect of Bokashi on improving the smell problem
Aim: To test if the addition of Bokashi can improve the smell problem, and have any influence on the digestion rate
Results
Images of samples with bokashi and water
On the 2nd Week of the experiment, moulds can already be found growing in all three bottles of the experiment set with Bokashi . Therefore, it is a failure and we stopped our experiment. We decided not to use Bokashi due to the growing of mould even though it improves the smell problem.