Prickly Pear Juice for Natural Building


The Prickly Pear Cactus
(view our full, final presentation here)

  • Native to the western hemisphere, but can be found in other places in the world
  • Found in abundance in Mexico, especially the central and western regions.
  • Also common in the Western United States, particularly arid regions in the Northwest.
  • It’s the only type of cactus that is native in areas east of the Great Plains.
  • Grows in areas of SLO County, making it an appropriate tool for this class.
  • Can have 2 types of spines: large, smooth, fixed spines and small, hairlike prickles (glochids)
    • Glochids can come off of the cactus and puncture the skin easily
  • One of the better types of prickly pear cactus to use in earthen plaster is the Opuntia ficus-indica


Problem Statement:

The current technique for extracting prickly pear juice is difficult and time consuming. We plan to first explore different methods to simplify this process. Eventually, we want to experiment with different ways of using the juice.


The resource we have= prickly pear, but what do we want to do with it? How can we get the juice?

Decision Matrices:

#1- Ways to Extract Prickly Pear Juice:

Criteria Construction Cost Consumer Cost Efficiency Practicality Safety Total Perfect Score
Weight 20 20 30 30 10 110
Absolute Weight 18% 18% 27% 27% 10% 100% 100%
grater 2 7 3 2 3 3.4 34%
boiler 5 8 4 6 5 5.6 56%
soaker 5 8 3 6 9 6.2 62%
compressor 6 6 7 5 5 5.8 58%
juicer 3 3 5 4 8 4.6 46%
dryer 5 5 3 4 7 4.8 48%

what we learned from our labs: We found that the grating and soaking processes were the most successful. These results line up with our decision matrix for the soaking process, but the grating process turned out to work much better than expected.

#2- Different Types of Prickly Pear Juice:

Criteria Construction Cost Efficiency (in process) Practicality Labor Effectiveness Total Perfect Score
Weight 30 40 30 40 50 190
Absolute Weight 15.8% 21.1% 15.8% 21.1% 26.2% 100% 100%
Soaked Juice (only) 20 20 20 30 10 100 52.6%
Grated Juice (only) 25 20 25 20 10 100 52.6%
Soaked Juice with adobe 15 15 13 15 40 98 51.6%
Grated juice with adobe 10 15 15 10 40 90 47.4%

what we learned from our labs: There may be potential for waterproofing with prickly pear mixed in with adobe, but our experiment was not conclusive enough to tell. More waterproofing testing is necessary.

What we have learned: (progress photos on these external pages)

Stage 1- Getting Acquainted with Prickly Pear
Stage 2- How to Extract the Juice
Stage 3- Fireproofing and Prickly Pear
Stage 4- Waterproofing and Prickly Pear

Group Interactions:

-feeling like we didn’t have a clear direction because we did not know what our next step was after we found the best ways to extract the juice

Group Dynamic:
Stage 1-
We got to know each other better when we had to collect prickly pear, and we had fun experimenting with the cactus. We found we were all on the same page with our approach to the project. We set a foundation for our communication by setting up a group text app so we could all text each other at the same time which turned out to be very useful and needed. It was also convenient that we were all in the morning lab together too.

Stage 2-
There was some concern over what to do next with the project. We were discontent having no distinct end goal and not being able to use the shop equipment. It felt like we weren’t finding new information and weren’t being useful.

Stage 3-
Our spirits were lifted because we were doing a more organized, controlled experiment, and even though our tests didn’t work/were inconclusive, we didn’t feel like we had failed because we were learning new things. GoogleDocs really helped with communication here because we could collaborate and update/create supply lists and to-do lists together and all access them.

Stage 4-
We all enjoyed being outdoors and working with something more tangible. It was great applying our knowledge of prickly pear to an actual project.

Conclusion/Where the project stands/possibility for future:

Continue with waterproofing experiments – creating a more controlled environment by making uniform bricks (1. with grated juice mixed in, 2. with soaked juice mixed in, 3. control with no juice), then the amount of erosion from the water can be better measured.

Group Members:

Gaby Antonova- I am a second year Biology student with personal educational pursuits in sustainability. I came into this class with an interest in gaining more technical background and continuing the exploration of appropriate technologies that I was exposed to in UNIV 391. I also have an interest in botany, so the idea of using Prickly Pear in natural building seemed like a valuable topic to explore. This class has been very unpredictable and has led to unexpected personal learning.

Courtney Jacobson- I am a second year Business major concentrating in Information Systems and minoring in Sustainable Agriculture. I came into this class because I have a passion for socially and environmentally responsible business and am interested in learning more about appropriate technologies. I chose the Prickly Pear project because I’ve had some experience with natural building and I am very interested in permaculture.

Lindsay MacLeod- Hello! I’m a fourth year Journalism major concentrating in broadcast, with a minor in Law and Society. I took UNIV 391 in Fall of 2011, and I found the idea of appropriate technology so fascinating. I love exploring natural tools that can help improve the quality of life for someone. The idea of a natural building tool is part of why I was so interested in working with prickly pear. Prickly pear is a cheap, sustainable resource that has the potential to help people! I love the freedom we’re given in this class to explore topics we enjoy and learn more about ourselves.

Anna Nagasugi- Hi, I am a fifth year architecture student with a minor in sustainable environments. I am passionate about using architecture as a direct tool to help others and I hope to continue my career on a path focused on social humanitarian design. I have really enjoyed working with other majors in this class so far because I think it makes the projects much more diverse. I chose to work with prickly pear because of it’s potential to improve natural building. I think it is great that it is natural, available resource that may be able to offer the same benefits of some non-renenwable, man-made resources. I am excited about the scope of this class because it has helped me to see our individual roles in helping the environment, where many of my other classes have been overwhelming and distant due to their large-scale, international focus.

Jenna Watson Hey, I’m a third year Journalism/PR major, very passionate about social justice issues- more specially women and gender issues. I’m very interested in cultural and religious studies and might be getting a religious studies minor along with one or two other minors 🙂 I’m interested in prickly pear because I think it is very applicable and an important part of environmental living to have natural building rather than more chemicals in our atmosphere. I’m hoping to learn new skills with our prickly pear labs along with being able to apply these tool/lab processes that I’m learning.

Comments/Suggestion Section:

Pete (March 26):
I like the presentation of your process. Prickly Pear may be a reasonable waterproofer. However, what it is used as (my understanding) is as a setting material for adobe… it makes a better final finish for the surfaces that resists cracking. Is there some way to investigate this in your test? Can I have a picture of the different adobe surfaces with a description of the process that gave rise to them?

I think you girls are doing a great job! The compression group found it very useful to try the differently “prepared” juices as a binder. Will let you know how it works out! -David H.

I like that your group is collaborating with the natural compressor group, I saw the prickly pear in lab and feel that it is a good way to combine the two projects! -Kimber

I touched that prickly pear stuff… ew!! I hope you can find a good use for it! – Sheila p.s. add some photos!

Some background information on what the juice is currently used for would be a beneficial to the readers. Pictures pictures pictures! – Shauna

Maybe check out some of the layouts on the other web pages to get an idea of how to make yours look a little less like a homework assignment and easier to read! -Pearce

Pictures would be awesome. I’m not really sure what a prickly pear looks like, so it’s hard for me to imagine what to do with it. Have you researched methods for extracting juice from other fruits? A lot of industrial engineering has been done to process food, someone may have already developed techniques you could use. – Sean

Have you guys made any discoveries or progress? I see every lab working hard to remove those prickles! – Oren

I like that groups are working together in this class and that resources are being effectively shared. Have you tried developing some type of device, similar to an orange slicer (, that would only slice off the skin of the pear? Obviously they are each different sizes, but if you had some type of spring that pressed the walls in to accomodate for different sizes that might help. There’s an interesting devices that cores and peels apples as well that the food science department has ( That might work pretty well. Then maybe the question would be how to develop a cheaper method of producing the corer/peeler. – Nichol-B//