An Algal Growth Journal
A journey in learning to grow microalgae at home
Around the beginning of the pandemic, I discovered the concepts of carbon capture and carbon sequestration. Since then, I’ve gone on a long, wonderfully fascinating journey delving into this part of the world of environmental science.
Carbon Capture and Carbon sequestration are methods to recapture excess carbon in the atmosphere. Global warming is caused by excess carbon that humanity has released into the atmosphere.
Along the way, I discovered the enormous potential of microalgae such as spirulina and chlorella as biological forms of carbon capture. One usually associates trees as the biggest solutions to environmental problems. However, trees (while absolutely still necessary for ecological preservation), are not enough to recapture sufficient amounts of released carbon. Microalgae instead, grow faster and can capture far more than fully grown trees in much shorter periods of time.
I wanted to understand the practicalities of trying to grow such microalgae in a domestic urban area (aka, at home).
It was a long journey that spanned over about a year, and a half and I performed the experiment under the guidance of Dr Suresh Kumar at KUFOS. In the midst of lockdowns in 2020, CFTRI, Mysore, very kindly sent me a small sample that I used to start my culture. At the time I that started and performed the experiment, it was extremely difficult to source lab approved mediums. As a result, with what I had on hand, as well as the few resources that I was able to purchase, I discovered my own mediums to grow it in. It was a process of a whole lot of trial and error.
I was ultimately able to take the initial culture of 30ml to about 2.5 litres over the span of a year and a half. It is possible to grow algal cultures in a much shorter span of time and in a much smaller space than what is required to grow a tree. The experiment was conducted in a small balcony. Admittedly, there is more fine tuning required to scale it up to the carbon absorption levels of a tree, but it is feasible.
My learnings through the experiment:
- The processes and principles that go into taking care of an algal culture at home.
- How to make relatively simple nutrient mediums to grow the algae in…as well as the disastrous results that could occur when there are issues with the medium.
- The factors that affect algal growth and the possible causes that can result in a decline in the medium, as well as ways to revive the culture in certain cases: I discovered how to alter the pH of the medium to aid the culture growth. I also figured out concentration ratios of nutrient to water and algal density required.
- In hindsight, I also realised that I really ought to have kept a separate culture to test out the algal growth when I decided to shift to a completely new medium from the one that I knew worked. It was that what ultimately resulted in a slow, drawn-out decline of the culture.
Below is a record I kept through the experiment. For the majority of the experiment, it was a bit difficult to see visible changes in the culture on a day to day, or sometimes, even week to week basis. Therefore, the entries did land up being sporadic at times. There were also personal challenges that came up due to which changes over long periods of time weren’t recorded as regularly. However, I did monitor the culture growth during those periods too.
Growth Journal:
AIM:
To show that spirulina can be cultivated in a domestic, urban area and to understand the challenges, and issues that could arise in the process.
OBSERVATION JOURNAL:
30ml of spirulina culture was received from CFTRI by speed post on 14 August 2020. The letter they sent alongside it mentioned that the algae should be kept in a well-lit place and it should be transferred to Zarrouk medium as soon as possible. Since this was in the midst of the pandemic lockdowns, it was difficult to source resources like Zarrouk medium which are typically used to cultivate it in the lab.
Started attempts at formulating a medium after finding some basic micro and macro nutrients at a nearby fish store. The macro nutrient was essentially an NPK solution and the micro nutrients were primarily iron, cobalt, copper, etc in a solution. A small amount of these nutrient solutions was mixed with water and this mixture was used as a growth medium for the culture.
Started the experiment on 15 August by adding about 7ml of spirulina culture to three glass jars (filled ¾ the way with the growth medium) and adding about 20ml of the growth medium to the remaining 10ml of the initial culture in the received test tube.
5 September 2020
About 3 weeks into first growing algae:
Initial two weeks of growth:
- No visible algal suspension in the jars, and hardly any green shade observed in the medium within the jars.
- At the beginning of this week (31 Aug — 5 Sep), dead, brown spirulina settlement was observed at the bottom. This was the first of any form of settling in the jars.
Current Hypothesis:
A possible reason could be due to a large difference between the ratio of volume of water to that of spirulina in the water.
The water (R.O reject water) used for the growth medium may have also had a certain degree of chlorine content in it which could also have affected the algal growth.
Although the jars were shaken at regular intervals, since the jars were filled three-quarters up, the water may not have been agitated enough, which could also have affected the alga.
- On 24th Aug, a fresh culture was made in three glass test tubes from some of the remaining culture in the initial test tube to make it easier to visibly monitor the growth of the algae. The growth medium used was made with R.O water instead of R.O reject.
- In all three test tubes, algal suspension was visible along with green settling at the bottom. Test tubes shaken regularly. Two of the test tubes didn’t show much settling. On shaking this settling combined homogeneously with the suspension in the water. In the third glass test tube, suspension was visible. However, the settling itself was very clumpy.
- Been adding 3ml of nutrient water each day to the test tubes since last week.
- As of 30th August, 7.00pm, the test tubes seemed as they had seemed all week. The test tubes could not be observed or shaken on 31st Aug. On 1 Sept, in the morning, two of the glass test tubes were observed with brown settlement at the bottom and no visible green suspension or settlement in the test tubes, indicating that the algae had completely died out in them. However, the glass test tube which had shown the maximum amount of clumping, and the initial plastic test tube had algae which survived.
- Over the past three weeks since then, the plastic test tube with original sample of culture (from the institute) continued growing. Certain amounts of the culture from this test tube were added to other containers to start cultures there, but fresh growth medium was added in its place.
- The different mediums used while experimenting with the other cultures were also added to this one. Although the concentration of algae in the test tube has reduced due to the dilutions, the algae within it survived relatively well. Clumping, settling and small amounts of brown algae also visible. However, the majority of it remains green. In the first week or so, the algal settling was primarily at the top. However, that settling has now shifted to the bottom of the test tube. Biofilm formation also observed at the bottom of this test tube.
Testing the pH of the growth medium:
The sudden death of the algae (in the glass test tubes) led to more research and some revelations. The growth medium was tested for pH.
> Spirulina grows in a pH of about 8.2–9.0
> The proportions of water and nutrient in the growth medium, as written on the nutrient bottle label seemed extremely off. So, the concentration of nutrients in the water now increased to test it out.
> The R.O. water used had a pH of about 6.7- 6.8. When the micro and macro nutrients were added to the water, the pH reduced to 5.0–6.1
> When only macro nutrients were added to the R.O water, pH increased to about 7.0
> This implied that the micronutrients made the growth medium acidic, while the macronutrients slightly increased its alkalinity. The macronutrients could not increase the pH of the solution by much. However, adding some tablespoons of sodium bicarbonate helped increase the pH to more suitable levels.
- As of 5th Sept, the two test tubes in which the algae had completely died were cleaned out and fresh cultures were started in them using the new growth medium made from sodium bicarbonate and higher concentrations of macronutrients, as well as very small amounts of the micronutrients. This medium has also been added to the test tubes with the still surviving algae.
6 September 2020:
- Among the two fresh cultures, one shows suspension but also has settling at the bottom. The other one is entirely suspended in the water.
- The glass test tube with the surviving algae, shows a lot of both dead, brown algae as well as live, green algae. It shows suspension but also has a lot of clumping that settled at the bottom.
- Very little biofilm formation or clumping seen in the test tube with the original culture. Settling of algae within the test tube easily gets suspended with a little agitation.
8 September 2020:
- The two test tubes with the fresh, alkaline medium are both visibly greener. Little settling is observed and it mixes easily on agitation. No visible clumping aside from a few small specs of dead, brown algae floating within the test tube.
- The test tube with the original culture shows a lot of settling. When it settles, the remaining water looks almost clear. However, a small amount of suspension is still seen once it settles. A lot of clumping is also seen at the bottom.
- The glass test tube with algae that survived shows a lot of both settling and suspension. The shade of water is between green and yellowish brown. A lot of settling does not mix in easily when agitated.
11 September 2020:
- In the two test tubes with the fresh alkaline medium, the colour has started taking on a slight yellowish tinge. Hence, some fresh growth medium was added to all the test tubes.
- The same was done to the glass test tube culture that survived and the original algal culture. The glass culture was a bit yellow and the fresh nutrient helped increase the green.
12 September 2020:
- Every test tube looks considerably better with the addition of nutrients.
- However, only the test tube with the original culture still has algae dense enough to be viewed under a microscopic lens.
13 September 2020:
- The algal settling in the test tubes has moved from the bottom of the test tube to the top of the test tube. This algal settling is at the surface of the water instead of the bottom in all the test tubes.
- There is some suspension also visible in all of them
- The glass test tube with algae that survived has also started taking on a deep green colour
- In all three glass test tubes, all live alga settles only at the surface of the water. Only specks of have dead algae settle at the bottom.
- The test tube with the original algae culture, has some live algae settling at the bottom, but algal settling at the surface of the water is also present.
Conclusions as of 30 October 2020:
- A combination of water, sodium bicarbonate and NPK solution to form a growth medium with a pH of at least 7.7 is an apt medium for algal growth at home.
- A small amount of fresh medium should be added to pre-existing culture every 4–5 days to supply nutrients to the algae and prevent it from dying.
- Healthy alga is one that rises and settles at the top of the container. However, it should be agitated regularly to keep it suspended in water for as long as possible.
- Higher surface area for air in the container results in better growth of algae.
25 November 2020:
- Gradually working on increasing the amount of culture
- Increased total number of test tubes (including initial culture) from 4 to 5.
- Also made fresh cultures in two glass jars and a conical flask.
- Slowly working on transferring the algal culture to a 5-litre tank.
- Now that the alga is growing pretty healthily, fresh growth medium added every 10 days or so. It is still agitated at least once a day.
30 January 2021:
- The alga is very temperature sensitive, and shows differences now that it’s winter. When temperatures drop the algae starts clumping and forms flecks through the container. The cultures in the glass containers also don’t grow as well, probably since glass is a good conductor. However, cultures in the plastic containers continue to grow well.
February-March 2021:
- Alga slowly transitioned to a 5-litre plastic container
- A basic prototype of an Arduino based automated agitation process also developed. However, it requires more iterations to make it sufficiently efficient.
April 2021:
- Algae is slowly moving into a high growth phase and is growing well
- Growth medium continues to be used. · R.O. water used as a base to avoid chlorinated water.
May 2021:
- Algae continuing through a growth phase
- At the end of the month: transitioned to a new medium of baking soda and NPK in the form of a pellet plant fertiliser. The NPK adds a strong brown-red tinge to the growth medium. The change in medium performed so as to try and reduce costs, when compared to the original NPK solution.
June to August 2021:
- Through June and July, the algal growth phase slowed down. It eventually appeared to go into a limiting phase despite the addition of nutrients.
- At the end of July, a fresh test tube sample was started from the bioreactor and put on the old medium.
- That bloomed strongly. But when the alga was moved to the new medium, it moved into a recessive phase.
- The bioreactor meanwhile just kept moving into a recessive phase. Biofilm growth was observed at the bottom but no new nutrients were added since there was a lack of the old growth medium.
27 September 2021
- The test tubes were moved back to the original growth medium.
- The bioreactor is showing signs of green growth suddenly despite no new nutrient addition. Fresh growth is also observed on top. The colour is similar to that of blue green algae.
- The test tube samples are slowly recovering back to a growth phase.
28 September 2021
- A sample of the green mass from the bioreactor appears similar to spirulina, but the samples are very clumpy and the zigzag spirals of the algae, could not be observed. This could also have been due to issues with the lens itself.
- Needs to be compared to a sample from the test tube
- Likely that moss has started growing or that there is a combination of spirulina and moss or possibly some other phototrophic organism entirely
03 October 2021
- Both bioreactor and test tubes show little change.
By late November-early December 2021, every single container that had been inoculated with a culture medium had shown one of two observations.
· Especially in some small test tubes, the algal culture to water ratio simply had been too low. As a result it died off quickly.
· In others, especially in the 5-litre tank, it clumped up and became a green mass. Under a microscope, a sample of this green mass did not show any of the characteristic zig-zag that characterised spirulina.
By mid-December, it was clear that it had been slowly contaminated by an aquatic fungus. There were large bubbles formed within the mass of green in the water and there were visible hyphae sticking to the sides of these bubbles.
CONCLUSIONS:
Considered several scenarios: The most likely scenario finally settled on was that the NPK of the new medium slowly attracted airborne spores of an aquatic fungi. The NPK may have also slowly caused a reaction within the spirulina itself resulting in a slowing of growth. The form of NPK used turned out to only be partially soluble in water. It needed to be fully soluble, and this was unfortunately, a late realisation.
